Swollen mouth on Rope Fish

:sick:
When it rains it pours! Just lost a fish in my 10 gal. Now my rope fish isnt looking so good...and I won't even go into whats going on the 5 gal. right now. So I've had Nessy, my rope fish for about a year. He has always been healthy and active, even though other fish in his 35 gal tank have come and gone. But yesterday, it appeared that his mouth was slightly swollen. There apears to be a bubble at the joint of the mouth on both sides, but more so on the left and the left upper lip seems slightly swollen. But then I thought, maybe I just never noticed this before. Sometimes I get paranoid and see things where there is really nothing. I watched him again today and am still unsure, so I'm checking out if anyone around here has seen something like this or might have an idea about a treatment if needed.

Thanks.

He is eating as enthusiastically as ever, but when I checked the water, which I admit I dont do often enough, I found the ph and Nitrate high, So tomorrow, I'll be doing some work on the tank to bring those numbers down, and hopefully that will help.

My ph is 7.5. It doesnt change alot, it just stays higher than any of my other tanks. I am embaressed to say what the nitrate level is. I have pretty much just been doing 5-10% water changes. I did one last week before I noticed the swelling. But clearly, I need to do bigger changes. I'll do a 10-15% tonight, then wait a few days and do another one and so on until I get it down...

I suppose it is possible he hurt himself while feeding. He tends to dive into a corner once he grabs the food and smash it around among the gravel or whatever is handy.

Is my bio wheel supposed to be turning steadily? It goes, then it pauses, then it goes again. It is also really old, but do I need to change the bio wheel? I change the filter as needed.