Big help please!

my plants are 3 weeks into flowering, i've been using Biobizz top week 1ml per Ltre of water, the leaves have gone VERY yellow on one plant and some of the others there are a few leaves that have changed. What should I do?

Also by the photos do they seem to be making good progress for 3 weeks?

some plants do that from lack of N during flowering. If it gets worse, I would try adding some more nutes to your mix. Just a little until you find your sweet spot.

so its not from too much nutes?

also do they look ok for three weeks into flowering??

can any one help pls?