If you're seeing brown, slimy stuff, that is likely zooxanthellae. Anemones will do that for a variety of reasons, at this point I would suspect it has something to do with acclimation to your tank. As the anemone is settling in, maintain very high water quality with regular water changes, activated carbon, and protein skimming. BTAs are quite resilient if you provide them with excellent water quality.
Also, could you post a FTS?