I think it's your alt diffuse. Check out the promo renders by morris for this product. Killing the culprit light or moving it skould help. You can also reduce highlighting in the script or in matroom. Great effect but not always desired... I would avoid filters. Nothing wrong with your rendersettings but for this, as is, Shading rate 2.00 and maxtex cut in half (even 1024) should give you the same results with more speed. Drop the shading rate for choppy hair as needed. I could be wrong...