Question about poop colour

[GrifTheGreat]

One of my frogs seem to be pooping white with blue coloured. The frog eats and poops normally, behaviour and setup is as it should be, diet consists of mainly redrunners (cockroachers) and crickets.
I'm really stumped. The only thing blue they come in contact with is reptisafe, my water dechlorinator, and I dilute it just right. (14 drops per 1.5 liters)
Also, if this was the case, my other frogs should be pooping white and blue aswell.
The poop is always solid, it disintegrated when I tryed to pick it up.

Edit: I do dust a little on the heavy side, and since the frog is litterally glowing with health but just pooping an odd colour, could the problem be overdusting with calcium and this in turn picking up the blueish colour from the reptisafe?
Either way, I'm going to reduce my dusting drastically and if the next poop still looks the same, I'm going to take it in for a fecal exam.

ReptiSafe shouldn't cause anything like that. It is most likely mucus. Never seen blue in their poop though.