My Betta is sick, help!

I had my female betta, Sunshine, in a 10 gallon with 4 Rosies (that pink feeder fish) and a small algae eater(unsure of breed).my tank is heated and filtered. I came to find 2 dead Rosies and a dead algae eater the other day. I removed the filter and exchanged 1/4 of the water. I have a well and my water is VERY hard and it takes a lot to soften it even a little bit. My Betta was a charity case. I found her forgotten in a green, cloudy, awful smelling container at the pet store and couldn’t bare to leave her.
The day after the fish died, half of Sunshine’s face had gotten fuzzy and her scales are lifted. It’s just her face by her eye and gill. I’ve given 2 doses of Ick Guard tablets. Am I treating the right illness??

No, she does not have ICH. She may have a fungus? But that would be a guess as I am not too sure.

Definitely not Ich.... Most likely a fungal infection. Many fungal medications out there... don't know which one though. Aquarium salt MAY be good since it supports the immune system to help fight it. I am not good with diseases/infection, so someone with much knowledge would be better.