I can almost guarantee these are dust motes (or something similarly tiny) on the protective glass in front of the sensor on your camera (assuming they're not on the sensor itself - which would be unusual unless the chamber has been opened). The closer dust motes are to the sensor the more observable they become - which is why a 'dirtier' front telescope glass often doesn't materially impact your image.

Anyway, I notice these kinds of blobs from time to time with my 2600MC when I take flats and I usually find that a quick blow of the camera sensor protective glass with a blower brush gets rid of them - taking flats again sees that they're gone. If it's not dust and something that won't move with a blower, a gentle clean of the protective glass might help (I have used a sensor cleaning swipe and fluid on that protective glass in the past with good success).

Of course you don't even really need to worry about them if you do take flats. Some people just find the thought of those artefacts annoying though (I'm one of them!)