Thanks, @Budwizer, I fixed it with Epsom and AACT over the week. Bounced back beautifully. Shot gents.
My soil mix was a bit too rich, so I broke it down with equal parts, coco, ewc, my soil mix & perlite. Didn't add lime for the extra coco. I think that particular strain was just more sensitive to the deficiency. IMO.
Ill monitor and Epsom salts as per @CG420za schedule above. Pic below a week later.