I have BTAs cloning and growing in my RSM which is just compact lighting.. this one looks small young and not yet accustomed to its new tank, yet.
Keep doing what you're doing keeping its water quality high and maybe while its inflated see if it'll eat some small bits of mysis or something about that size and it may help its recovery too.
Sometimes they do need greater light but you'll see signs of bleaching. That one looks colored but not colorful, maybe its recovering from a bleaching event that happened before you had it. Hard to tell. Usually anemones just take a lot of time.