Sick Julii Cory

[LTurner97]

I cleaned my tank yesterday and did a 25% water change, I noticed last night my Cory had a red blotch on its side and when goggling it suggested to do a salt bath for 15mins and return the Cory back to the tank , done this and this morning the red blotch has gone however still one very unhappy Cory sitting at the bottom clamped fins and hasn’t eaten today , upon looking further in the day he seems to have a graze in the same spot but it also looks white ? It’s not just a white looking spotting like ich it looks like a graze , still hasn’t moved much from same position since morning and breathing heavy , I’ve checked parameters but only with a dip stick as that’s all I have atm and they all read good any help or advice what could be wrong with him