Sick Catfish- stopped eating..

Hey I’ve recently posted about my Lima Shovelnose Catfish but things have slowly gotten worse and out of ideas. I’ve had this Lima for over 2 years. About 6 months ago, I started to notice some amoralities of his Anus( see Pictures) Also the last 6 months he has been shedding his slime coat alot( at least I’m pretty sure that’s what’s happening) Until a couple months ago he was acting normal though. He use to eat bloodworms and got very excited when I dumped them in the tank. Today he won’t even move when I use bloodworms let alone eat any. So I went to feeding him krill and as long as you put it close to him he would eat. As time went on I had to soak the krill in Garlic to get him to eat and the last couple weeks he won’t eat at all. Sometimes he grabs the krill but spits it out. I've tried feeding live guppies and he use to go crazy for them swimming all around the tank hunting them but now he has no interest in them and won’t move at all. One other thing to add is I’ve had him for over 2 years and he’s not a lot bigger then he was when I bought him. I don’t think this is normal and he seems to be a very slow grower. Overall his appearance is good ,fins are good, eyes are clear. He’s in a 90 gal. No ammonia, no Nitrites, no Nitrates. Only thing to mention as far a water goes is PH is 8.8 or higher( tap water in Iowa is high though) Any Ideas or suggestion’s would be much appreciated.
For the record I tried Prazipro a few months ago thinking it could be a parasite. No luck. If by chance it is a parasite and the prazipro didn’t kill it, could he live with a parasite for 6 months or would it have killed him a long time ago. Thanks so much for help

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Update: My catfish has been picking up the krill and seems like he is trying to eat. once he has the food in his mouth he starts to act really weird. He thrashes his head, spits the food out and re grabs it, and every time he does this he also sheds his slime coat. He acts like its a real struggle to try to eat. So far he still wont eat he gives up after spiting it up dozens of times. Any ideas or suggestions.??? Please help!