that's showing calcium deficiency but goes on to say that it generally starts in newer (younger) leaves whereas mine is occuring on node 4 and lower. Also those spots look more ambery-red (like rust) in those pics, my spots are more of an earth-tone brown.
to add info, I made the mistake of giving them blooming nutes when I thought the power had gone out (tripping them to flower mode) but reverted to vegging light times. I used two different products. Shultz Bloom builder (5-30-5) and Plantprod Flowering fertilizer (15-30-15). I used relatively small doses. Here's a couple more pics of some new shoots. They're fairly yellow towards the stalk of the leaf and greener towards the edges. Going by this thread here -
https://www.rollitup.org/marijuana-plant-problems/157345-have-plant-problem-check-here.html
I'm leaning towards a nitrogen and potassium problem because of the wrong nutes being used at the wrong time. Is it a simple matter of going and getting veg nutes? Or should I flush first? I had planned on tripping over to flowering when I get my 400w hps next weekend.