What is your water change schedule?
You say it's a community tank but what else is in there.
Pop eye, which sounds like what your Pleco has, is a symptom of an underlying infection. Do you have a quarantine tank you can isolate the pleco in?
I would recommend large daily water changes and be sure not to overfeed.
75: blood parrots, featherfin cat, emperor tetras, turquoise rainbowfish, BN plecos, japanese trapdoor; 46: WCMM, gold inca snails, ghost, bamboo & amano shrimp, kuhli loaches, rummynose & ember tetras, endlers, platies, flame gourami, guppies; 16: pygmy, peppered, loxozonus corys, otos, assassins, RCS ... ~ Research PRIOR to purchase.... ~