I have a sebae & have had it for a long time
. Sometimes they can take weeks or even months to get use to your tank & water conditions. It sounds like its just not fully inflating all the way around this is normal or it may be unhappy with the lights, but without a picture its hard to tell. I can tell you that sebae's need light & lots of it anemones have zooxanthellae & this is what needs light they are photosynthetic so light is a must. BTA's need the least amount of light, I havent heard of anyone keeping a sebae long term in a tank under pc's I have seen live for near 1 year with dailly feedings under pc's, they can live a long time without proper lighting but sooner or later it will bleach. When I got mine it was 3" & in about 5 months under 500watts of MH lighting its now over 8" & is a dark healthy brown. They dont need to be feed often once or twice a week, or under poor lighting then at least every 2 days is a must. I feed mine raw shrimp & mysis shrimp about once a week. Is it sticky by this I mean if some food were to touch it would it stick to it? I hope this helps!!!!