Thx, for providing this data.
You have a lot 'nvidia-settings' processes running in your 'After top' output. This could be the reason for the performance drop.
Just to add my voice to this list, I'm also an SMOS user experiencing the same issue. HOWEVER, it's only on my 13 card 1070 rigs (H110). I have a 6 card 1060 rig (Z270-A) that has been running for days with no drop in performance, also on SMOS.
Thanks for being responsive!
UPDATE: For me, the problem seems to have gone away with v0.5.7. 24 hours solid now with no performance dropoff. Added 2 more 13 card rigs about 8 hours ago and all seems solid.