Gorilla Glue Auto 1

Definately magnesium deficiency. It looks like it was an older issue possibly caused by overwatering your seedlings/young plants.Adding cal/mag starting week 4 is typically best in order to add enough for when they begin to bloom. It's unlikely the effected leaves will correct their color issue but all new growth should be fine. If you still have an issue you can spray a solution of 1/4 teaspoon epsom salt(magnesium sulfate) to 1 quart water spray this to the point of dripping off the leaves be sure to get the undersides of the leaves. Once weekly. Until symtoms go away. Do not spray your plants while under direct light. Or you can use 1 teaspoon of epsom salt per gallon of water as a root drench. Adding too much calcium can actually cause a potassium deficiency which is needed for bud developement. Lastly establish a strict wet then dry type watering cycle to avoid nutrient absorption issues. Hope this helps.