Cockroach "dust" ?

[HexaDiplo]

Some of you may have seen this picture before on another forum.
I have a hissercockroach with white dust coming out from the joints on his back. Is this spores from fungi or something else? My other three cockroaches do not have this dust.

 

[Draketeeth]

I had a male with this problem. Always assumed it was a grooming / activity issue because once I got him in an enclosure with more roaches, the issue went away as he became more active and socialized.

Could be wrong, but whatever it was never affected his health as far as I could tell. He's still part of my colony.