Thanks a lot.I think I will just start all over

Hi nairalanders my name is walshak ,my catfish are two months old,an I rare them in a plastic tank,a month ago my problems started when I experience d several deaths.it starts with white patches ,peeling skin,and then they hang at the top and die.have been bathing them with antibiotics,salt and ash but there has been very little improvement. Just today I four one more dead body.I need help pls