Bottom leaves getting chlorosis

Swim....thinking my friend has a phosphorus deficient setup, but help clarify this inquiry, please. Lower leaves always turn yellow from seedlings on up. Temps are consistently in the mid to lower 70's region...indoor. After week 2 we notice a slight yellowing of the lower leaves then they wilt and continue to get worse. He uses well water that runs a bit in the alkalinity range of 7.0. Completly organic soil base. Some nutes are added at 1/4 to 1/2 dose every 2 weeks. Any suggestions what might be the issue before taking the next step?

Thanks.

Pics would be more helpful....could even be Nitrogen deficiency but impossible to really know without seeing it.

Prob N deficient. They tend to canibalize the lower sections how you describe to send nutrients up