White pasty substance from vent. Any ideas?

I had a past customer/ client email me this morning thye following: Hope you can help me and shed some light on a health situation concerning the turtle I purchased from you. Our guy is growing like a weed and doing great from that aspect, but the past week or so a tape-like white discharge has been showing up everyday. I took this into the vet for inspection and she sees no worm DNA in this sample. However, she wants me to bring in a stool sample to test for parasites. There is a Zinc style test that would reveal 100% of potential parasites, but that is not available at her location right now, so she would run one that would give a 75% spread of potential parasites. She said it would be nice if I contacted you since it was home bred to get some experienced information. Have you seen or had this problem before? Or can you offer any information that would help us in the right direction. My son loves taking care of this guy and enjoys watching him. Please help if you can…the vet would like to pick your brain…so if I have your permission, I will give her your email or call her at