whats going on with my baby? 3 weeks in flowering and yellowing of bottom leaves COCO

hey guys im around 3 weeks into flowering, the flowers on her are looking nice and beautiful but there is a problem. On the bottom of her leaves, on both of my plants the leaves are starting to turn turn yellow and veiny. Heres a picture what do you think is going on?
BTw im in coco

I don't see a picture..

is that better?

Hi I have exactly the same problem as you 3 weeks into flowring and 1 of my lowryders' lower leaves turned yellow almost over night. What type of light are you using some one told me that if you are using envirolite red (flowering) you should add blue occasionally to keep leaves green. wanted to know if you are using envirolite aswell. hopw we can both fix our problem