Probably the potting mix you are using..They are drowning in a sea of plenty of moisture and therefore the roots have stopped functioning

You probably have root rot, which is what Mike, above is saying. The soil you are using is probably responsible for that because it retains too much water. I doubt that your trees are going to survive, but it may be worthwhile to repot them into the mix described below:

My version of Al Tapla's 5-1-1 Mix

· 5
parts pine bark mulch (remove ½” pieces through 1/2 inch screen)

(Some people use Repti Bark instead of
mulch. This does not require screening but may require more frequent watering.)
Be sure to soak the bark overnight.

· 1
part sphagnum peat

· 1
part perlite (coarse, if you can get it)

· 1 Tb garden
lime /gal 5-1-1 mix (measure the 5-1-1 mix)

· Osmocote
plus (follow manufacturer’s instructions). This is optional.

·
Moisten well and wait at least 2 days before using

contrary to popular opinion, rocks in the bottom don't help drainage.

So what have you done for this tree? Did you follow through with this great advice, or did it die?