use root tabs sparingly otherwise they run the possibility of burning your plants. i use no root tabs and use pfertz macro/micro's every other day. None of the plants other than the red ludwigia (which needs fe) require ferts but the quality of light is important. Ludwigia will tend to stunt and start to melt if heavily shaded.
Water Wister is a plant of paradoxes. it can live and spread under the worst conditions but have delicate and sensative leaves. Ive kept these guys smothered in a quart container full of plants without any holes burning through it.
Crypts generally melt by shift in water params so im not going to touch on this but im guessing you might see the plants getting too much ferts at the root level. Just a wild guess since we dont know the dosage, planting proximity or type used so its just a guess. you'll certainly see an improvement with a water change.