I've seen these spots on my cleaners, too. Not too sure what they are. They don't seem to impact them in the least. They don't "break open" like you'd expect with an egg sac (e.g., parasite larvae, etc.) They're just there. They go away with the next molting. I've got one cleaner that gets them about every three or four moltings. I've had that one for a few years now.
Have fun,
Jaret