my problem

my problem started about 6 months ago with spots on the leaves that looked like a calcium prob..turned out to be a root rot prob..I grow in DWC I had this prob about 8 years ago and started using Aquashield cut off the infected roots plant got strong and life was good..now the prob is back..I was still using Aquashield..I thought maybe it was something to do with the ferts...tried a few different ones no luck ..tried bleaching everything and started new clones..a couple weeks later the prob was back..I thought maybe it was something in the tap water I've grown with for 15 years bought a R.O. system..cleaned everything with bleach , new clones a couple weeks later the prob was back.. threw out everything I grew in wiped down all the walls started new clones...a few weeks later the prob was back..water temps mid to high 60's room temps mid 70's small clip on fan running all the time ..6 inch exhaust fan runs all the time..here a couple pics of the new seeds...and yes the probs back..one of air into the container with the babies the other of the roots of the largest seeds...2 are Bruce Banner, 2 are Jack Herrer, 2 are Hawaiian Purple..and yes they all have the prob.. I'm out of ideas ready to try coco but before I do any ideas