All 3 GPUs will run on build, but ONLY 2 at time?

Hey all, I use the following build mostly for gaming, but want to make the best use of the gear in off hours mining.

In my primary PCIE slot I’ve got a 6800. I’ve added a 6700xt and 6600xt to do some mining. All three cards work on this rig, but I can’t get all three to work at the same time, only 2. Any thoughts would be appreciated.

ASUS B550-A Gaming Mobo
Ryzen 5 5600
16gb G.Skill Ripjaws
Powerspec 850w
Corsair 750w

Got all 3 GPUs running on my gaming rig.

It was really strange, the 6700xt just refused to be detected from a riser. I ended up connecting the 6700xt directly to the board and put the 6800 and 6600xt on risers (same riser and slot that wouldn’t work for the 6700xt).