I am talking about my potted cuttings in the cups

Too much water, not enough water or  not enough light

Are all the leaves yellowing, or just the bottoms?  Are the leaves turning uniformly yellow, or just parts of the leaf?  Also, what type of mix are you using in the cups? 

If the mix is a soiless mix, like perlite/vermiculite and you have a good root system, it might be time to start giving them some fertilizer.  Nitrogen deficiency would be a common cause of leaves yellowing (usually, from the bottom up) on the plant, and other nutrient deficiencies can cause yellowing, also.  If you have a good soil mix, you typically don't need to fertilize for quite some time since the plants can use the nutrients in the soil.

what is a good soil mix for the next stage of 1-3 gal pot?

I use Fox Farm Ocean Forest when I up-pot my rooted cuttings to 2-gal pots. Its organic and works very well for me. Good stuff.

will any organic ready soil mix for pots is good?

George, IMHO, I think your fig is fine.  All the new growth looks good, and in my experience, it's not uncommon for a plant to drop some of its lower leaves as its growing.  If that first leaf sprouted indoors, for example, and then the plant was moved outdoors (or into stronger light) where the second and third leaf sprouted, the leaf that first sprouted may just not be accustomed to the new environment as the newer leaves would be. 

The seed starter mix should have some nutrients in it, but it is mixed 50/50 with the perlite and in a smaller container, so it is possible that it's running shy on some of the nutrients, especially if it's been in the cup for a while.  It's definately mature enough that you can try adding 1/4 or 1/2 strenght fertilizer mix just to make sure it has everything it needs.  If you notice the yellowing start to spread up the plant to the newer growth, I would definately start looking more closely at nutrients and PH, since the PH can effect the plants ability to uptake the nutrients.

thanks for the advice

First of all, it is very common for a cutting's new leaves to fall off, so I wouldn't worry. 

The seed starter I've used is mostly peat moss with perhaps a wetting agent.  As such, it has no nutritional value for plants.  On the other hand, fig cuttings don't really need nutrients until they are well established and in sunlight.  They are using stored energy to produce roots, leaves etc. 

If the cup was very dry, it may well be due to not enough water.

But my recommendation would depend on how extensive the root system is.  We can't know that since we can't see it.  But you could take a sharp knife and carefully slice off a bit of the bottom part of the cup to see what's going on down there.  If there are many roots, I would do the following right away:

1.  Transplant into a 1 or 2 gallon pot.  Use potting mix + perlite rather than seed starting mix.  Potting mix has some nutrients in it so it will feed the plant.
2.  Make sure it's getting enough light.  That could mean either placing in a sunny window, or outside in a shady area if it's warm enough where you are.  If you give it too much light to soon, the leaves on it now will probably sustain damage.  You have to do it gradually.
3.  Consider watering with a weak fertilizer solution, no more than 1/4 strength.  Probably not necessary, but if it's weak, it shouldn't hurt anything.

thank you for your help