Nock, does not look that bad to me, mild desentary. When bees are clustered due to cold, they have to hold it, no bathroom breaks until warmer weather permits. So in a cluster with thousands of bees in such close proximity and inability to relieve themselves, small amounts of dysentery are not alarming. Nosema, one probable cause, appears to be always present in the bee gut. For reasons described above, the Nosema spores accumulate under such conditions.
Now, if the outside or inside of hive was almost solid brown with splatter, then I would worry. We have a fella here, The Honey Pump I consider to be an authority on Nosema. The fella actually does spore counts with microscope and slides. Hopefully, HP can chime in and shed more light on the subject. There are other beeks on this forum that can offer there knowledge also, better than I.
For now, I don?t see any serious worries.
Enjoy the Holidays
Van