I have 8 figs in 1/2 gallon containers that I started from cuttings in February.  They were originally placed in damp perlite in bags, then moved to 50/50 perlite/vermiculite in 16oz plastic cups. When I moved them to the 1/2 gallon pots, I combined the mix from each cup with the soil (decomposed granite) where I intend to eventually plant the trees. The first month in the 1/2 gallon pots, they did GREAT. They put out 2 or 3 big leaves each, which were all a nice deep green and looked supple and healthy.

Although they looked healthy, I stopped seeing vigorous growth. So, a couple weeks ago, I added a teaspoon of Dr. Earth Kelp Meal to each pot... I thought that was a conservative amount. 

About a week ago, all of my lush green foliage turned yellow! Was it the fertilizer? The only other factors I can think of are that we had one really hot day... about 90F.

These figs are very precious to me. They were started from the fig tree I grew up with, which was started from my family's tree in Sicily. Is there anything I can do to help my babies recover? 

I'd rinse off the soil and repot in one of the recommended potting mixes.  Ultimate potting mix or fafard #52.  Members here report good success with them.  Let them recover before you fertilize again.  That much kelp sounds like a lot for a 1 gal pot but I'm not familiar with that product.  Potted plants get something like 1/10th what you'd give an in-ground plant, baby plants maybe even less.

The directions on the box call for 1 tablespoon for a new planting in a 1 gallon container. Maybe these little guys just weren't developed enough to handle a normal dose?

It could be many things.  A sudden increase in sun light, too much or too little water for the soil, The soil particles are too fine, herbicide spray from a neighbor, maybe things I haven't mentioned.  I used a fish emulsion/kelp extract exactly as directed and the next am all the plants I put it on were dead.

Since they aren't doing well and you live in an area near a lot of well stocked nursery supply outlets, my guess is putting them into a proven soil will maximize your chances of saving them.  Photos of the plants and roots would help as well.  Close-ups of the nodes, too.

Here's some pics. They don't look that yellow here, but they are compared to the dark green they had a couple weeks ago.

Low iron if the leaves are old. 
Low nitrogen if the leaves are young. 


http://ag.arizona.edu/pubs/garden/az1106.pdf

I bet the soil and perlite have separated and created stale conditions that are causing root trouble. I would plant some out asap and have a look and repot the others before things get worse .

Plant some out? As in open ground in the orchard? I have been considering that. I would love to get them in the ground ASAP. The weather is certainly warm enough. Most of the directions I've been following seem to suggest keeping them in pots for the first year. I'm not really sure why. If I'm going to have to pull them out of the pots anyway, might I go ahead and put them in the ground now?

remove all soil raise and repot. If it continues then it's a nutrient problem. Your soil is most likely missing something or is having too much of something. 

This is from the UC's Specialty and Minor Crops Handbook Pub 3346:

Personally i would keep that plant in its pot and in the shade and not add anything to it nor pull plant out of its pot.
Folks tend to overthink things and add this and that do this and that and stress the plant further.

Many times a plant will go stagnant for a period of time for whatever reason and if left alone and put in shade they do fine.

From the looks of it your tiny plant looks like the sun is beating it up.

agree with martin. leave it alone. put it in partial sun or shade. don't fertilize. see how they respond. water only when the container is almost dry, but not completely. you should be able to feel the weight, when the pot is very light. personally, i don't think they look all that bad.

too much sun too quick can do that. lack of fertilizer will do that. but, lack of fertilizer will not kill the plant. it will just slow down. when fertilizing the cutting, i wait till they are in 1 gal and i give about 1/4-1/2 of MG. then again, i used MG seedling soil and MG perlite at 50/50. i stopped using MG perlite, not because they cause issues for me, but i got bulk perlite without any additive for rather good price locally. MG products come with bit of fertilizer already in them.

Well, that 90°F day occurred just a few days before they yellowed, so that seems more likely to be the problem. I only gave a half dose of 1-0.5-2 fertilizer... I wouldn't think that would be strong enough to burn it, but then I am new at this.

Aside from any issues they are experiencing now, will they generally do better in the ground versus pots? I have four acres of good soil (Fallbrook is famous for our excellent soil) with irrigation. Seems to me like being in the ground will give them better insulation against extreme temperature changes.

Yes they will absolutely do better in the ground. Potted figs will never reach the same size or productivity as those in the ground. Soil in "the ground" works because there is good drainage and bacteria, fungi, etc that keeps the root zone nice for the tree. Soil in a pot holds water and will not let it go, then shrinks when drying and separates on rewetting.

Bury some of the pots a couple inches into the ground and watch as the plants take off in a month when they send out roots into the soil. Potted and unfertilized plant with root issues will just sit there, dying.

2 out of 3 plants I see are suffering pretty badly. The one with green leaves might be OK to leave alone for a while, but why risk that it will follow the same path as the others with the same conditions? 

"I never worry about action, but only inaction."
Winston Churchill 

I just wanted to follow up with the outcome on these figs. I decided to observe them a while longer before doing anything. They actually started to perk up a bit. No new growth, but the leaves seemed to be regaining some color. Then, we had another hot day and the leaves yellowed again. Seemed pretty obvious to me that the yellowing was caused by too much sun/heat. I moved them back further under the eaves so that the only got an hour or two of direct sunlight. They seemed to like that a lot. However, still very little growth, if any.

Finally, I moved them up to 5 gallon pots. This time, I used REAL potting soil. The stuff I had before had very little organic matter. The perlite/vermiculite is not really soil at all. The decomposed granite that I mixed in is more like sand than soil. Ever since I put them in bigger pots with soil, they have developed several new leaves along with stem growth!

I haven't put them directly into the soil yet because I want to keep a closer eye on them. I keep them right out my bedroom window, so I check them every day. I'm afraid that out in the open, they might get dried out or grazed on by our stupid goats.

So, in summary, I believe I had two separate problems: 1) leaf damage from too much sun and 2) lack of growth from too little nutrition

good to know it worked out for you. i try not to disturb the roots as much as possible with any problem. once root is disturbed, the stress can set back the plant for a month or more leading to taking further unnecessary actions that can kill the plant. but i'm sure there are times when repotting is the only option.

I agree with Dieseler, and bullet08, to put them in the shade, and do nothing else...I was given a Col de Dame Noir back in March/April and it was a beautiful green color and doing well...then the bottom two leaves turned yellow and eventually fell off, so I talked to the forum member who had given me the tree(very experienced member)and he said to put it in the shade and give it a rest, and it recovered nicely and now has put on additional leaves and about 2 1/2" of additional growth.

Glad they got better for you!