is this a cal/mag deficiency? leaf pic included

what should I do to remedy this problem? started a week ago, today seems to have spread to a lot more fan leaves.
plant is GG4 seeds from Igrowingmarijuana.com. indoor, LED grow, end of 4th week of flower. soil amended with perlite and garden lime. I flushed last week with sledgehammer because A. At end of 3rd week of flower ff soil chart says to, and B. the brown spots on the leaves were noticed
after flushing i let it dry out for 5 days. then watered with just epsom salts.dried out fast(2 days) then continued feeding at 1/2 strength the ff trio 2 days ago. thought it was magnesium def(that's why I tried the epsom salts. didn't seem to help. i've read that GG4 can be magnesium whores so seemed to all add up. i have 2 plants and this is only affecting one. any response would be great, thanks!
ps. the sick plant with the spotting is on the left, it's also more of a lime green than it's darker green sister on the right. same seeds, same everything

Im not an expert but I’ll respond. Looks like a cal mag deficiency. I would feed the cal mag with normal nutrients. I think using Epson salts and lime take a while to release

Phosphorus deficiency

Need some more p and k and less n im thinking maybe. Im not an expert but had a similar problem and upd my feeding of p and k and went bk to normal.