Id hold off medicating. Truely doesn't appear fungal or bacterial and if viral can't treat that anyway. You really shouldnt use meds unless certain of what yourr dealing with. External parasite med would be ok to try tho as they are easier on the fish. Tank sounds perfect. Id keep it bare bottomed for a while but maybe toss in some elodea to rest in or hide. It does great uprooted and will help with water quality. Keep on top of the water changes and wait and see. Any new symptoms get back to us. He seems from your description to be acting normally. Keep him on a good varied diet and clean water. It just may resolve itself. Healthy unstressed fish generally can fight off nasties on their own given proper care and time. This does not seem at this time a time to use antifingal or antibacterial meds as it can knock the fish ( meds are tough on the body, namely kidneys) and really shouldn't be used unless you're certain of what your treating. Some aquarium salt might be helpful as well.1 teaspoon per 5 gal.
all the best
cheers