Well if you could find that 75-100gal soon I'd set that up immediately and use your current tank as your QT
. For the health of your fish u need to upgrade immediately. Your lion is already quite large 7" (18cm or so) a 40gal isnt going to be big enough in the coming months especially with the grouper..
Triple Sulfa is a bacterial fighting medication that can erradicate cloudy eyes.. you might want to try that.. Fluff knows alot, so hopefully you listen to her and the others on here..
I believe the fish will only continue to get sick unless you upgrade immediately..