popping sound
i'm no expert either, and this example may prove so, but when i first started collecting snakes i started off with a baby ball python. the retarded pet store lady told me that he would look beautiful on white sand. well, within two weeks i was hearing a popping sound coming from its mouth. when i started seeing white bubbles around his mouth i took him to the vet. the vet gave him some medicine and told me to get a new substrate. i did, and he got better. so, it's possible that what iris said may be true. may be a respiratory infection. couldn't hurt to check that out.