Help❗❕What's wrong with my pleco?

[supersarahh10]

He has a white spot on his back. I looks like he's literally loosing scales, but I kno that's not possible. I'm so worried about him. I've googled it & no1 can give me a definitive answer.

 

[Andy Sager]

He has a white spot on his back. I looks like he's literally loosing scales, but I kno that's not possible. I'm so worried about him. I've googled it & no1 can give me a definitive answer.

That is a wound that has gotten infected. It very well may have been caused by the other catfish in the picture. The pleco should be moved to a hospital tank and medicated with an antibiotic to help the wound heal. If you need help on setting up a hospital tank, I have outlined it on post #2 in this thread: Quarantine tanks and Hospital tanks, are they really different?
You will need to know the pH of your water to know which antibiotic to use as not all meds work or work best in every condition.