Any chance of a clearer pic? I know you said it happened over night but to me that looks like severe fin rot and now body rot. Of course gourami and betta will fight but it looks like too much damage to me.
I don't think it's worth taking another picture. It looks like he's nearly gone; just floating on his side but still breathing. Is mouth to mouth possible for fish?
I wasn't keeping him with red tipped sharks, I know they can't be trusted.