Weird brown dirt reappearing on carapace

[TheLastGreen]

On my hingebacks carapace, on the same spot a soil like substance keeps occuring the last two days. He's on orchid bark, and I can't figure out where this keeps coming from?

 

[Yvonne G]

That looks like dried poop.

 

[TheLastGreen]

Thanks Yvonne, I scraped it off yesterday but perhaps it didn't wash off completely, was scared it was some sort of fungus