I just googled hole in the head disease and it doesn't look like that. The hole in the head disease is small flat patches, whereas this is one hole that is fungus-like, and spreading. He also had a patch on his right gill but that's healed up well, the one on top of his head is just getting worse.
He hasn't been near any ladies lately, so no rough play going on there.
As you can see, he's a very sad fish - he doesn't eat much (if at all) and has had this condition for weeks
I just had a thought, when he was sick and bleeding, I moved him to a small hospital tank, he responded very well to treatment and enjoyed being on his own. He had been with a deformed angelfish which sits on the bottom of the tank for a while, but I'd since added a baby pleco and bronze cory. I added another male fighter and put him in a guppy tank until I could get a tank set up for the new fighter but he got out - and it wasn't long after that that the my red boy got sick. New boy is aggressive, my red one isn't.
I may have put him back into his tank, from the hospital tank prematurely (even though all the others have been moved out, except deformed angelfish which had been with him for ages before anyway with no problems) but maybe just being back in that tank is enough to upset him of what happened before?
I'll set him up in a new tank this weekend and see if he improves then. I've tried all meds possible, including applying meds directly to the white but he's not improving.