Hi everyone, it has been a while since I have posted on here, and now I am posting because of some very ill luck with my 120g. How bad is this situation? The 120g angelfish community tank has been giving me trouble since some time in October or November, and I'm considering dumping/restarting the entire tank, or maybe just dumping it. I am worried that euthanasia may be in at least one fish's near future. I posted twice on the The Angelfish II forum during these past few months, but they have not helped me with the latest issue.
It's really quite an effort to type out the whole story from its beginning in the fall, and I think I scared potential advisers away the last time I did that, but you can check out one of my previous posts
here.
Note: I'm a college student, but I have been maintaining 2 or 3 tanks at home despite going to college - the 120, a 33gal, and sometimes a 5 or 10gal. I go home every other weekend (literally, I alternate weekends between campus and home; they allow up to 10gal tanks in dorms, but regulations explicitly forbid swimming pools in campus residences, so I can't pass off a giant aquarium as a pool

) and do a 50% water change on both larger tanks. When the 120gal started having issues, my parents started doing additional weekly water changes (when I'm not home for the weekend). The 120gal has a Rena FilStar canister filter.
Despite losing a few angelfish without any visible symptoms prior to suddenly becoming lethargic/occasional erratic swimming, I am considering the eyes issues to be my biggest problem right now. It's certainly harder to treat something when you have no idea what the heck it is. My gold angel has fuzzy brown growths in each eye, which started out as dark spots without obvious texture/mass. The growth is only the inside of the eye, I guess it's called the anterior chamber? It appears to be avoiding the pupil, instead growing on the surrounding silver area (a fish's iris?). However, it does appear to be growing outwardly, and I'm afraid it may push through/rupture the cornea. I suspect that the angel already has trouble seeing food at the surface, although it still makes the effort to eat.
The platinum angel that suddenly started suffering from unilateral popeye weeks later - I immediately added epsom salt to reduce swelling, but it is still kind of bulging outward. There are 2 dark spots under the tissue, above the eyeball, and I'm wondering if that's the same thing affecting the gold angel, just in a different area of the eye.
I first tried treating the eyes with PimaFix/MelaFix since that surprised me last time. I have no idea if the brown eye growth is fungal or bacterial, or if it's gram positive or gram negative bacteria. In other words, I have no idea what to treat it with. Medicine is burning a hole in my pocket & having ZERO effect, so I'm considering calling it quits.. at the very least, I am worried I will have to euthanize the gold angel if its eyes get too bad. After the MelaFix/PimaFix, I tried dosing the tank with Maracyn 2 (guessing that Aeronomas might be responsible). Nothing. I'm almost done with the following round of Maracyn 1, again to no effect. The medicated flakes did nothing, as far as I can tell. I dose the tank at half capacity, 60gal, which is still pretty expensive. I don't remove the visibly sick fish (2, at the moment) to a quarantine tank because I'm worried the other fish are also infected (like the few that died rather suddenly).
While I feel personally responsible for my fish, and I would miss this hobby if I gave it up entirely, these past few months have been incredibly frustrating and disappointing. I have spent, for me as an individual, a considerable amount of money, and lost more fish than I have saved. So, I'm hoping someone here has some good advice, or at the very least knows someone else I can ask.

If you didn't read that link, at least take a look at the pictures of the gold angel's eyes. The attached pictures are relatively old, I took them 2-3 weeks after the dark spots first appeared. Now, the growths have increased in size so that they connect to one each other and are way more visible. It stresses the poor fish out to have its picture taken, but if someone thinks they have an idea & needs to see more, I'll try to post updated pictures.