Bat guano needs to be added at the beginning of grow or at transplanting to it’s final space because it takes a long time to release it’s nutrients into the soil, so it will do nothing but drain the wallet at this point.
Buckets like that are indeed not really great plant containers. They allow light to reach the roots, which they don’t like.
I don’t exactly think it’s a K deficiency in the soil, but more the plant’s inability to take it up. Either way, if you flush with a mild nutrient solution to flush out excess salts, you won’t harm the plant if it does turn out to be a K deficiency. Other way around, if it’s a salt issue and you keep feeding it extra K through the same SIP process, you are further concentrating the salts in the medium and your problem will keep increasing regardless of extra K being fed.
So whatever your chosen path, the results will show what it was by the accompanying plant response.
