A question about my plecostomus

Question
I read that neosporin can be used on red sores. I just wanted to confirm that. I have a plecostomus that has a red ish pink area on his head where it looks like the scales have been dried out. There are several red sore/wounds that appear like they have been bleeding. He has gotten worse and only slightly gotten better. We've been treating Fred with antibiotics and have had no luck. We think that he may have been injured by another fish. The spot is not getting any better although it's getting any worse. We wonder if it's a parasite, but we have two other plecostomus and other fish, and they do not have any similar symptoms. Any advice you can give would be greatly appreciated and helpful. Thank you for your precious time.
10 gallon tank, water change (25%) and vacuum once a week, temp 73-75 F, algae tablets and tetraColor Granules once a day, Three roseys, one goldfish, two plecostomus. water levels-pH 7.2, Alkalinity little high, nitrite/nitrates safe and water is hard

Answer
Hello Kelly Ann,
Unfortunately your tank is a little overcrowded.A Goldfish and Plecostomus both in a ten gallon tank is far too much fish and not enough tank.
I would recommend upgrading to a larger tank (30+ gallons, depending on what kind of pleco you have), it will allow your fish to live longer and actually reach adulthood, as well as make it easier for you to keep them alive. When is comes to aquariums, size does matter.
I don't think neosporin is fish friendly, but you can use aquarium salt as a natural remedy, along with Stress Coat slime replacers, it will help a lot.