Critical purple and pineapple 2nd grow

Looks like a magnesium deficiency. "As a fixed nutrient, any drawback, as a rule, is manifested in a new growth of the leaves. Yellow spots appear on the leaves, which over time become brown, causing dying of the leaves. Areas between residents of old leaves yellow (exclusive chlorosis), and stains can also appear. Colors of rust. If not treated, magnesium deficiency can seriously reduce the ability of plants to assemble the harvest of any type. "

After looking though the last 4 or 5 weeks, i think we have ourselves an honest to goodness magnesium deficiency.... interveinal chlorosis and rusty spots starting to form on mid plant leaves. You only fed at ~630ppm and couldn't have been oo far above that in any recent week, if not whole grow. epsom salt or cal mag. how much depends on how much is in what you regularly feed. The other pictures give a much clearer view. It's early stages and looks way worse under your grow light than it is. get Mg ppm up around 80 and S-100+, Ca - 100ish. this wil depend upon the water you use... e.g. i have fairly hard water, so you may need more. n/p/k - 120s/50s/190s will do you good