hello! my plants are in flowering day 37 and i not...

Hey there @pixsna! You are experiencing interveinal chlorosis. There are two types of nutrients in a plant Mobile and immobile ones! Mobile ones are able to be moved around the plant and applied where needed while immobile nutrients cant be moved. The plant stores its nutrients in its leaves and when it lacks a certain mobile nutrient (like nitrogen) in the new growth it pulls that nutrient from the most effective area (most likely old growth). If the nutrient that is deficient is an "immobile" one it cant move the nutrient to the new growth so a deficiency will show itself directly where the problem is at. This is why paying attention to WHERE on the plant the deficiency is happening is important! If the yellowing(chlorosis) is occurring from the bottom up then its a nitrogen deficiency if the problem occurred from the top down you have an immobile nutrient deficiency that is causing your interveinal chlorosis. First thing I would look at is your PH make sure its not to high as this hurt most immobile nutrients. I hope this helps bring some insight. Please update us on the source of the chlorosis so we can better diagnose this plant. 😎 (If were looking at a N deficiency there isn't much you can do as the damage is essentially done)