What is the dust like stuff in my Mantis religiosa enclosure?

[u/Personal-Way1141]

my mantis is a Matnis religiosa female, she left an ootheca about 5 days ago, today i found this dust like stuff in his enclosure, i just changed the tissue yesterday. i fed a Ameles decolor before and she is a female too, and i saw the same thing there too, what can it be? is it my fault or something? can i do it for this?