This was back in week 7 of veg, any ideas what mig...

All previous answers my be right however sometimes lower leaves dont get the light they need,and will then cannibalize the said leaf to use the resources elsewhere in the plant. So don't sweat it your plant is doing it's job. If it had continued yellowing that's a different story. IMO 👍

Looks like you had a bit of a phosphorus deficiency that later cleared up when you started using nutes. If that is actually the case I would question your soil as the plants were way to small to be having that problem at that time

A 7 week plant in a 1 gallon pot? you are way overdue a transplant (2 weeks overdue I would think), and the soil is fairly depleted of nutrients. I'm not so sure it's Nitrogen deficiency, since the yellowing is not homogeneous and those dark spots make me think more like a Potassium (K) deficiency. Anyway, if you want to keep them in a 1 gallon pot, you would need to feed early.

Nitrogen deficiency ,try use for 1-2 days water , or lower your dosage of nutrients prob will help you :) have a nice day

This to me looks more like over-fertilizing. For me the best is 1 fertilizer 1 water. Much water and a revive/root solution after water or with the water i think it would be great. Anyway as i see them is no reason to worry. It looks like you will have a great harvest!

Nitrogen deficiency will cause older leaves to yellow and die off and eventually fall off

This looks like a phosphorous deficiency. How often do you feed your plants with nutrients and how often do you give them plain PHed water? Anyway this seem to be solved since your plants are healthy and beautiful. Enjoy your harvest!