Hole in the head

[Proteus]

My Sohal Has developed a patch above his eye. small but still noticeable also looks to be a little swelling. now I did just move some rock and he did get stuck a couple of times so im not sure if its a wound from him freakin out while i rescued him.lol

my tank is 130 gallon so lots of swimming room and diet is a mix of daily misas and or cut up shrimp, and macro every other day also eats NLS pelets daily, food is soaked in cod liver oil and garlic guard and occasionall Selcon. water quality is good I did have a Ph drop and a spike in amonias but that has been dealt with,the only other issue is KH is at 190. i have just made a 20% water chaange and removed the carbon from my tank.

Please give me a little insight as the only write ups found are based on cichlids in which says most part is ue to water quality and poor diet.