About 1 month ago, I had two koi who stopped eating and were breathing heavily. I treated the pond with Aqua Prazi and 3 days of Microbe-Lift Broad Spectrum. Now 1 month later I have a different fish with similar symptoms. I'd like to retreat the pond with the same products but don't know if this is advisable given their recent use and concerns for the fish developing a tolerance to the chemicals. On the other hand, I don't have a lot of options.

Any feedback is most appreciated.