Hello, so it all started like, forever ago when my brother got two frogs for this stupid kit for land frogs. He got to Africans, Zazu and another frog who's name I forget... Anyways the first froggie died

and Zazu was left. Then came Dj, replacement for the frogger that died. Zazu then died after my brother never changed their water unless I threatened to take them or something. Zazula (Found she was a girlie! Dj is a male.) became so extremely skinny and emaciated and she passed. My brother just brushed it off and continued to ignore lonesome Dj.
So I finally got him to hand over Dj after convincing him he was neglecting him. I noticed that Dj, who when Zazula was alive was very fat, is now emaciated and skinny. My brother used to plop one crab pellet in there a day, but I got him some real ADF food and have been giving him three. I gave him three last night, when I feed Yuuki and Ryu and Beau and Kia and Echo. He has not eaten any yet, and it is about 3:30. He has been near them a lot and I know he knows that the food is there, I need help. Please help me to get him healthy again, thank you!
Tank size: 1.5 Gallon
Plants: Anubis plant, Marimo Moss Ball
Decor: One cave
Heater?: Yes, his tank is heater, however I don't think the heater is doing anything. His tank was colder than my Goldfish's.
Extra: Has a bubbler
Filter?: Yes it has a filter
Lighting?: Yes I use the tank light and my desk lamp
Feeding: Used to be given 1 Crab Pellet, now gets 3 AFD pellets
Health: He is generally healthy despite not eating and his skinny-ness. He is active though and sometimes chirps
Tank mates?: No, his tank is too small for me to add anyone