sores

For a few days now, almost a week one of my cherry barbs has been developing a lump on her side. Here are some videos of her.. 1. Size of tank? 50 gallons 2. Water parameters a. Ammonia? ~.05 [a little high, i know, b. Nitrite? 0 c. Nitrate? 5ppm d. pH, KH and GH? 6.4, i drop, 2 drops e...