Lime green shoots and rusting on leaves (new to growing)

Hello peeps!
Hopefully someone can help me, I have 2 lovely ladies named lulu and Cher and to begin with I got them as clones age 5 weeks in a small pot in good healthy condition. The gentleman who i got them off advised me that they are ready to be repotted so i potted them in a 30cm pot but i since I am new to this I have made a couple of mistakes the compost was peet free and already had fertiliser in it which they did not like at all as it did not drain very well, it also caused nute burn but have over come both issues with new compost and flushing them both. Cher is 18inches and lulu is 16inches, I decided to flower lulu a bit early so started the flowering process 4 days ago so she is on 12/12 now but my problem now is the new shoots on Lulu are starting to turn a real bright green almost yellow looking at times, should I see some kind of change by now eg buds coming leaves changing colour?
My ph is 6.5 and I'm using natural day light, no lamps, mircle grow flowering solution and a darkened cupboard for the 12/12 cycle.
Any idea's if I am going wrong and a solution to fix the problems
Thank you lovely people :) ;)