Try adding SubCulture to a soil grow, with lots of perlite and good frequent waterings- that would be my choice were I to suffer that problem. Also, Serenade can be added to your res.
Last, the NFT style is an interesting choice for a situation like yours. The constant aeration and washing action over the roots, plus the fact that the water is constantly moving across a filter (you can add extra filtration to help remove dead shit and pathogens), helps prevent buildup of dead cells and rot from setting in.
Hope that helps?