Fish Disease

[Sands]

Hi me again, posted about my lown loach who died now one of the three remaining fish..a black widow? has one pop eye amd one v cloudy...this must be to do with the heater failing and bugs breading..I have done two 50% water changes and put Myxalin I think it is called in the water....not sure what else to do..also kept the light off so as not to stress the fish..Any ideas advice welcome..thanks