Nah, it doesnt have to be a deficiancy, and theres no gaurentee its not lock out either. If hes not emptying his runoff and its reabsorbing it could be lockout caused by root zone saturation, not ph lockout. Theres always a ton of things it could be and with only a picture its tough to really diagnose any problem 100%. All you can do is try and narrow down the grower errors the best you can. He said his lights were at 12 ", now thats too close. Fix. Theres a good chance hell say he has no idea what the ppm hes been running is, so that needs to be taken into account. Plants dont come with dip sticks and its even harder through a screen to tell, so ya.