Well, I have to say, my first impression when I saw that picture and before I read Drizzt's reply was that it looked like the "leavings" after a snake breeding. It has "that look" and being gel like also. My thought is that either one of your snakes is not a male as expected to be, or one of your males got "excited" by the other male and the high hormones during breeding season and left a puddle behind. And, yes, if you have two together, it makes no difference if one is not feeling up to par, they would still breed if they are of opposite sexes. The primeval urges at this time is a bit stronger than the yucky feelings of being a little under the weather.
Of course, I am saying this by just seeing that picture and not in person so it could be a defecation I guess, I just have not seen one like that myself.
Actually, if one regurged, it may be prudent to put that one in a "recuperation" container till it is back on it's "feet" again. Just to be sure that it is getting the rest and quiet time and extra TLC it needs seeing as a regurge takes a lot out of a snake. This is not written as a bash to you on keeping them together (although I personally wouldn't suggest that to anyone) but just when ill it seems prudent to do this. This way also, you can be sure you diagnosed the right snake as the sick one and can make sure it gets the extra TLC it needs. Just a thought.