All my prints are printing dark on my 3800 since I upgraded my Mac to high sierra and installed the latest version of QTR. I have been using QTR for several years on hahnanmule museum matte paper with great results. Now these very dark prints.
Re-install quadtoneRIP. This will fix you permissions and should fix the dark issue.
Otherwise it’s a gamma problem with the system. Printing with Gray Gamma 2.2 (Perceptual) mode could fix that.