I have a couple Celeste Improved plants & the stems have gone limp & many of them are dropping before they are ripe. None of the other 30+ varieties I have are seeming to do this.  Thoughts?

How old is the tree?
Is it in ground or in a pot?

These are the two details everyone will need to know to help you out.

2 & 3 years old in 5 gallon pots.  Actively growing, not root bound.  We've been having huge temperature variations, high 90s one day, lows in 50s the next.  I was thinking the trees might be responding to that.

A common trait of some strains of Celeste is fruit drop when immature (less than 5 years) and fruit drop when grown in pot culture.  Temperature and water - according to some - play a role in whether drop happens or not.

If the stems are limp then the roots are not pumping water. Are all 30+ trees grown the same way? Maybe the mix has smothered the roots or dare I say it, maybe they have rkn. = O