Help with dying furcata rainbows

I woke u to 3 dead furcata rainbows this morning. Now I have a couple rainbows that have what look like sores on their bodies, both in the same place about half way back the body. One is now swimming vertically with its tail down. No other fish seem affected and water parameters are fine. I've been reading and I thought it was bacterial until I saw the odd swimming, this is my first problem with the tank and I'm really not sure. I also have inverts and scaleless kuhli loaches in the tank. The only thing that's changed recently is i gradually turned the temp up to 82-84F because some of the rainbows were scratching against leaves and driftwood and I was preparing to battle ich. I'm also running a large bubble wall to increase aeration. Any help is greatly appreciated.