Could quite possibly be the clear filter on the QHY8 nosepiece. To see closely you'd need to check in good lighting or daylight.
See this link for similarities
http://old.astrodon.com/oldsite/LearningCurve.html
I used a bunch of cottonballs one at a time(not turning over to prevent finger oils getting on the swipe side) with mineral turps to wipe and dry out the clear filter window.
Now frosting is a real pain in the pants. I luckily one night had just the right humidity indoors to do a quick CCD clean and reassemble to use outside without further issues. When you see frosting you'll first think, Ooo pretty snowflakes... damnit!
Found a flat from the QHY8C, Im pretty sure at that time the many motes where from the primary mirror. At the time I had a focal reducer in that caused some curvature as you can see with the motes around the edges. I'm pretty sure the smaller dark mote at the bottom was dust spec on the nosepiece window. Goin from memory here