sulfer or magnesium

Im thinking sulfer or magnesium. they almost appear leathery and deformed/twisted leaves. 5 gal DWC currently being flushed with 5.9 water. 75-77F started to get root slime a 1 weeks ago. flushed with 5.8 water and microbe tea (https://www.rollitup.org/dwc-bubbleponics/361430-dwc-root-slime-cure-aka.html) Just washed out res 3 days ago and been uing 5.9 ph balanced h2o. Water temps do tend to run on the higher side of 72-72F. Have been throwing in frozen water bottle to help with res temps. Any imput appreciated

really need to control that rez temp very important with dwc the root slime is blocking the roots from getting the nutrients it needs get it below 68F and your golden. I would also get some cal/mag solution, I personally use GH CalMag works really well should strengthen those leaves up