The fish that are dying all start with the small ICH like spots?
I have had weak Bettas that I purchased who have ICH and fix them up easily with heat and a bit of salt. Each time very easy to beat and never comes back. Fish always recover.
For ICH to kill it has to be very severe and for a fair bit of time feeding on the host.
I suspect this is something else. I wouldn't be raising tank temps that's forsure.
I have had weak Bettas that I purchased who have ICH and fix them up easily with heat and a bit of salt. Each time very easy to beat and never comes back. Fish always recover.
For ICH to kill it has to be very severe and for a fair bit of time feeding on the host.
I suspect this is something else. I wouldn't be raising tank temps that's forsure.