yellowing leaves

hi RIU, my plants are about 7 weeks into flowering, and one plant has started to yellow from the top, not sure what it is.Thanks for any help.

sadj,
Not too many flowers for 7 weeks in. And the other leaves look pretty dark green. What nutrients are you giving them?
JD

^^^^What he said^^^^

sadj,
I decided to finish my thought from yesterday. Looks to me like you're giving WAY too much N containing "grow" type nutrients for that stage of growth. That will discourage bud formation, cause the dark green leaf coloration and you probably have toxified your soil with nutrient salts and are locking out normal nutrient absorption. Hence the yellow leaves.

So stop those nutrients...flush the roots and just give water for a week or so and restart low (or no) N "flower" nutes with high P and K...and easy does it on the flower nutes too, since we already know you have a tendency to overdo it...
Questions?
Cheers,
JD

thanks for all the info, my soil is a mix of Rock dust, fish blood and bone, and other stuff. i have never added nutreints. but i realise my soil mix needs to be revised, and thanks for input

would it help to add that i forgot to water them for about a weak? i usually water when they need it every 2-3 days but was preoccupied this week.

sadj,
Lack of water would cause a limpness of leaves and branches...but if it recovered well once you watered it, no harm was done. Medicalcenter may have something there on the zinc issue. With such a limited and non-traditional grow media...it might be short by a micro nutrient or two. I don't quite know what to suggest that you do. I'm thinking that a good flush might help...and certainly wouldn't hurt. Give that a try...
JD

thanks guys, i will try adding zinc to next watering