Nutrients or something else?

first, deal with the lighting, the light presses and then there are power problems

Issues with trace elements/minor nutrients (immobile nutrients) like manganese, zinc, iron, copper, sulfur etc, show up in the new growth first. Issues with macro nutrients (mobile nutrients) like nitrogen, phosphorous and potassium, show up in the oldest leaves first. I would say you have an issue with not enough potassium for this stage of grow.

My guess is a manganese deficiency or lock, due to a ph too high.. Manganese is best absorbed in an acid solution and it's immobile, so you see the problem on the old leaves. My advice is to turn pH under 5,8 for 3-4 days at least and then swing between 5,8 and 6,3 max. Good Luck