Always this f***ing is happenning to me. Each grow I have this same problem and i can’t solve it or I can’t understand it. To much nuts even i go really easy on them, or is a root problem? Need all the answers possible girls and boys!!!
This looks like magnesium deficiency. Check ph. If ph is good. Supplement cal mag.. when deficiencies like this show it usually means the lack of magnesium/calcium as started a while back. They don't take long to fix but can take a while to show
Do you suplement calcium magnesium or only vedge and bloom.. when usinh coco nutrients cal mag is often added in the mix, but when using vedging and blooming specific product a suplement is often needed the more the plant developoe into fliwering the more it consums calcium for growth.
Hard to say since I can't see what you are feeding them, but I would suggest checking soil ph first and make sure its 6.5-6.8. I would also be using just plain ph'd water every other time. Happy growing.