Hello, I have a 10g tank that's had no problems for about 3 years until now. I have 2 female bettas, 2 corys, 1 mystery snail, some live plants, and 2 recently added African dwarf frogs. I do partial water changes monthly (by gravel vacuum) and check water quality a few times a month - nitrate, nitrite, chlorine, ammonia, pH, alkalinity, hardness all within the "safe" zone, and tank is mechanically filtered, heated to 78 deg. F, and supplemented with aquarium salt. About three weeks ago I changed two things - I added two African dwarf frogs and switched my fish food to frozen brine shrimp and/or frozen blood worms from a common packaged brand that says they're disease/parasite-free. Since then, the health of my tank has PLUMMETED. 1. betta 1 developed severely ragged fins with spines sticking out, grotesquely swollen lips, tiny (almost can't see) white spots on face and fins, 1-2mm lump under right pectoral fin 2. betta 2 has pinhead-sized white, round protrusion on side of head. 3. cory 1 has white tuft on nose that appears to be spreading 4. nitrates and nitrates rocketed and are in the "stress-unsafe" zone of my testing kit and stay there despite more gravel vacuuming and partial water changes... 5. fish are swimming normally, appear to be eating fine, and only betta 1 has lost some weight (I think due to difficulty of feeding with ragged fins and swollen lips) On advice from a local pet store guy, I tried treating with Maracyn and Maracyn Two for the full 5-day cycle but no change. I purchased Maracyn-Oxy and am planning on trying that. But...WHAT IS GOING ON?! - why is my tank suddenly terribly diseased + has toxic nitrate/nitrites? Can frogs cause this? Or the change of food? Or something else completely? Also, I've been removing my frogs and snail when I treat because I don't know if it's safe...is this necessary? ANY help very much appreciated because I have no clue.