Has anyone had this happen to them and what does it mean?

I've seen this 3 times now, twice my crested a 1 year old male housed alone, has seen or been excited by food and basically passed out some bubbley, brown liquid which he promptley licked off. It is a small amount of direha but more runny. Sorry if this is gross. But is there something wrong with my crested?

Thanks in advance, ask any questions if you need clarification