Well as long as it eats and what not, it just may be how it is. Like I said mine bubble up sometimes then it doesn't for a while. Main thing is that it's healthy.
All anemones are different. I has both green tip and rbta and they do what they want when it comes to shapes. My grrem tip would chnage from bulbs to strands but rbta usually are strand like. It all depends on how much water they absorb and the amount of times they eat.
Check your water perimeters and did you move powerheads around? Some dont like the high flow and what are you feeding it. like cat said I would be concerned if its hiding in a cave for a week.