brown spots but no bugs

Hey guys i need some help I have 4 plants in a grow box in a storage room they were all doing well but a few days ago i noticed one of them, the second tallest out of the two tall and not to bushy from pcs in my profile has 5 fan leaves curled up with brown or rust areas, also i few more starting to get spots on hem they look like freckles, but there is other growth on it thats doing good, bit the top two fany lea, ives tips are curling inward but the infected ones curl up, e mite be a magnesium deficiency i went ahead and flus the plant real good today then added some epson salt standard ph fix amount 1/4 tbs per quart, then i mxed a sray bottle up with a small amount of crushed up epson salt some sinc sukfate and magnisium oxide are alread any ideas

need a picture. but judging from your leaf on ur profile picture its lacking phosporous

rust freckles sounds like calcium def,but a picture would help us to give you a better answer.

phosporous also has necrotic spotting on the leaves, plus the purple stem

Leaves that taco up are usually magbesium deficient. "They're praying for magnesium". My opinion is add some cal/mag. Cal/mag+ for the iron even better. Do you use tap water?

It was too late but cal/mag made all the other look great, the diseased one is still growing but luses every other bigleaf, even on side shoots i super cropped the top and the top 6" look awsome also i did some side sprouts then when they where big enough after the nuckle i took cuttings, to clone.