Your water quality needs to be improved and you wouldn't have ulcers.
Understand aeromonas, pseudomonas pathogenic bacteria
http://www.practical-water-gardens.com/pyjamas/article003.htm
This product may help your fish
Microbe-Lift Sabbactisun
A unique, herbal, immune-enhancing stimulant which reduces bacterial and fungal infections in fish with bacterial dropsy, fungus, milky skin, raised scales, fin/tail/mouth rot, bulging eyes, and ulcers. Helps to drive pathogenic bacteria off of fish. Stimulates and accelerates regeneration of damaged tissue until no trace of
the wound remains. Safe for all pond life in and around it. 16 oz. treats 240 gallons for 10 days.
http://www.koivillage.com/medications/microbe_lift.html
This product would help your pond.
KoiZyme
http://www.koicarekennel.com/About-Koizyme-c-2.html