I agree with Greg about getting the lime in now. That should be #1 on your list along with putting the hammer on those small bass. I would guess that not establishing a good plankton bloom prior stocking the tshad last year contributed as much as anything to the lack of survival. The lack of plankton (food for shad) and abundance of weeds (ambush points for bass) probably doomed them from the beginning. If your alkalinity is low you cannot establish a proper bloom, no matter how much fertilizer.
-HH