Both disks are showing data corruption (disk1 also read and write errors):
Mar 14 13:59:36 Unraid kernel: BTRFS info (device md1): bdev /dev/md1 errs: wr 35, rd 175, flush 0, corrupt 57, gen 0
...
Mar 14 13:59:40 Unraid kernel: BTRFS info (device md2): bdev /dev/md2 errs: wr 0, rd 0, flush 0, corrupt 504, gen 0
This suggests a hardware problem, start by running memtest, then there are some recovery options here.