IT gone off food, not looking his best

Hey guys I've posted about a similar subject, but now my tiger has stopped eating. He's got white edges to many of his scales, has recently gone off his food, and started flicking. What do you guy think I should do?
Water temp is 28 degrees Celsius, I do a 25% one to two times a week, tank is heavily planted and I have pothos growing out the top so nitrates are very low.


Sent from my iPad using MonsterAquariaNetwork app

Tank mates are discus, royal panaque, cactus pleco, palmas bichir, sun cats, BGKF. Trying to post pic. But it won't load for me. Will keep trying.


Sent from my iPad using MonsterAquariaNetwork app