Alright...for starters the other night i euthanized my cory because he had no fins and 2 giant red sores on his sides, i didnt want it to spread...well i might have been to late. I looked at my barbs and one of my barbs now has a blood red face. I checked everything, nitrite 0, ammonia 0, ph is 6.0 but has been like that for a while. WHAT IS WRONG