Hello I am relativley new to keeping aquarium and have recently added a few plants (a marble queen and a few italian vals) to my tank and my italian vals seem to be turning brown and falling apart and I am worried about the ammonia shooting up! I have a 20 gal. with a 17 watt t5 flourecent bulb and have it on for 8 1/2 hours a day. Any tips or suggestions as to what is wrong?

(PS i have 3 guppies 2 small catfish and a ghost shrimp in there currently)

Thanks in advance!