Are my plants okay? :(

Hey everyone, I posted on here about a week ago trying to get an answer to my “black spots/mold on leaves” problem. Some people said it was a potassium issue to supplemented it with composted banana peels and also some nutes which I’ll picture below. The black splotches are still coming back and also on my biggest one the entire stalk and all branches are turning purple?? I have heard that could be a magnesium issue but the whole damn stalk? I thought that only applied to branches… anyway please help me and my babies if you can! :slight_smile: