Does SRB have any issues running 13 gpu's. Try to switch over a rig with the Asus b250ME w/ 13 rx550's it does the intial load, but then the screen where it would show all the cards then load kernals stays black with a blinking cursor
have you try old version srb ? i thing new version any bug with rx550 series
if driver supports 13 gpu then SRBMiner supports 13 gpu. There are guys here using it with 13 gpu's.