Sorry for your lost. Its not a fun way to start off chameleon keeping...but we all have/had a learning curve. All you can do is go on from here.
Do you have any photos of the chameleon from the first week you got him?
You said you have a fountain...they are hard to keep free of bacteria and we usually recommend not using them....sorry. a dripper and mister/misting system are what is usually recommended. Make sure you run bother long enough that the chameleon drinks...they are slow to figure it out.
You said you use a red light for heat/basking....no colored lights are recommended. I would replace it with a white light...a regular household incandescent light bulb of a wattage that produces the right temperature in the basking area is what many of us use.
You said you use fake plants...if you have a veiled they eat vegetation so it's recommended that you use real non toxic well washed (both sides of the leaves) plants. It helps with the humidity too.
You said your cage is on the floor....I would raise it up several feet.
For feeding/gutloading you can use in addition to what you mentioned, dandelion greens, endive, kale, escarole, squash, sweet potato, sweet red pepper, zucchini, and a small amount of fruit like melon, pears, berries, etc. Lettuce has little value in the diet but in small quantities is good for hydration. The veiled chameleon's can eat these same things in addition to insects, of course...cut into appropriate sized pieces.
Looks like you've done some research already...lots to read on the forum here that will help your next chameleon do well!
Good luck!
I really appreciate it!
