That would be the liquid(I actually can't remember the scientific term for it ) that they use when grooming(specifically that's for cleaning the mouth area), you'll see them run their legs by their mouth, and almost look like they're chewing them sometimes. It's just them keeping clean.
That's perfectly normal, "An intestinal discharge of fluid cleans
And there's the science I was missingThat's perfectly normal, "An intestinal discharge of fluid cleans
them off the platelets and to the outside regions of the mouth, where the spider removes them with its pedipalps." last sentences of paragraph 4 basically fluid to clean off debris from an episode of feeding etc.http://atshq.org/articles/Digestion.pdf
Those deli cups need to be properly ventilated, there should be a few rings of ventilation around the sides, just a couple on the lid to prevent condensation. Having the venting only on the lid means it will dry out significantly quicker and not hold any kind of micro-climate....too much top venting is a serious detriment to raising slings especially.This is the photo...