Fish Expert Needed!

I have a 25 gallon tank with just 3 inhabitants. One is a good sized Pleco, the other two are basic barbs. I had a Botia, but it died & I did not notice the carcass for a day or so. About 2 weeks later, I noticed one of the barbs had bulging eyes.
I did a half tank water change, added some aquarium salt, treated with Meracyn II for 5 days. There is no change at all in the fish, & the other 2 fish seem fine. I assume if it is contagious, the other 2 fish must already have it too.
I did some research on pop eye - Everything I read is vague on the subject - from the causes, cures, whether it can be transmitted to the other fish - or even ME. (Tuberculosis from a fish?) Many offer little hope.
Can anyone tell me if there is anything else I can or should do, or do I simply let the fish die & hope my other fish will be OK?
I am hoping an aquarium enthusiast will have some experience with this disease/condition - whatever it is!
Thank you~
Julie