Have you checked your ammonia, nitrate etc levels? Sometimes cloudy eyes can be from ammonia burns. Try changing large amounts of water as often as you can. It's not a sure fix but a good starting place. It could be a bacterial issue or something else. It's more a sign (symptom) than an actual disease.
How long has your tank been set up? Was the tank cycled before you added fish? & how long have you had these fish? What is your maintenance schedule? How much & how often?
To me, & some of us here, melafix is not the best option. I understand wanting the least "dangerous" treatment...but it may be the least effective. Sorry, just my opinion, I've never tried melafix. That said, most treatments take more than 4 days to show any signs of healing.
If, in a worst case, their eyes don't get better, blind or slightly sighted fish can lead fairly normal lives in our tanks.
I have not kept your species, maybe someone else has better advice.
Good luck! & let us know what happens.
