hello this seems to be happening to all my plants. i am and experienced grower and never had this happen like this. this happens in veg and evrytime i go to 12-12. im using roots organic soil original.and some other plants just promix. is it starving? i have a cheap soil meter that test fertilizer levels. but i was told that they dont work. but its reading low on ferts. my ph is fine. for the roots organic saoil im using fox farm line. and for promix im using advanced nutes line. any help on this would be great. i thought with roots organic soil i wouldn't have to feed much am i wrong?
No, it's a macro deficiency. Your plants are seriously starving for Phosphorus, at the very least. You need to supply a great deal more than you have been. They may need more Potassium as well but there's too much P-def damage to say for certain. Don't be afraid of nutrient burn. For every one grower that actually burns his or her plants with too much food, there are dozens who cause much worse damage by withholding nutrients. Personally, I always make a point to slightly burn the lowest small leaves by harvest time so I can be sure the plants were fed as well as possible. Also, keep in mind that plants need stronger doses of fertilizer as they get larger. The existing damage won't heal, by the way. Once you correct the malnutrition issue, the damage just won't spread further. You should experiment a little during the next run. Before any deficiency damage occurs and makes it harder to notice burn symptoms, increase the fertilizer concentration until you start to burn the leaves a little. Nutrient burn starts at the tips of the lowest & oldest leaves because they're closest to the toxicity in the soil. Here's an example of Phosphorus deficiency:
I learned this VERY early. This is my first grow and I was going really light on the nutes. It didn't seem to affect my girls until I had a pH issue due to a faulty meter. The damage move way too fast to try and wait it out. Moral for me: make sure you FEED them! I stop feeding just short of a burn and that's one trait I've definitely learned to identify. G/L fixing your issues OP.