Thanks for all the advice. I have ordered a bottle of Bio-Bizz Alg-a-mac which will be here this week. I also gave the sick one about 3.5l of grow @2ml per L plus a teaspoon of molasses (just from the supermarket) tonight and the other one i got about 4.5L into her with a fair bit of run off - made a mess when i moved her

I am using the soil PH probe in the pic which is showing between 5.5 and 6.5 in most places and have ordered a PH pen.
Question - should i get some cal mag as well as the alg-a-mac? If so whats a good brand and should I add it to every feed.
Next feed will be due on Friday I think.
PS i think the second one is just starting to yellow but I am hoping I got to it early.