I have three bettas. Yesterday, my halfmoon(Sushi) died from what I believe was a fungal infection. It started with white, clear-ish, fungus growing out of his gills then it slowly spread pver his body within three days. He quickly became lethargic and just stayed wrapped around his heater. He refused food. I used API's Furan-2 for bacterial fish disease for the last two days of the fish's sickness. Now, not even day after my halfmoon died, my other betta(Custard) has the same fungus on his scales, not in his gills though. He is struggling to swim, his head can stay up but he cant control his body, and he is not eating. He is trying so hard to swim and be active but he is just getting worse. Both fish are/were in 5 gallon tanks with a heater, but no filter. I do 50%water changes every 4-5 days. Any advice or recommendations would help. I've had this fish for over two years and I have already lost one, I do not want to lose another.