Yes. They often deflate after grabbing food or at night. As long as they are fully opening again it is fine. If they stay shriveled for long periods without opening, or the mouth gapes, more of a concern.
I have a kessil a80 on a 13.5 gallon, I put it in the tank, it moved about 2"s from where I sat it and that's where it stayed. But sometimes its gorgeous & sometimes it looks all shriveled.
Can you describe your set up? With such a small tank, it's hard to keep parameters consistent, which may explain why the nem may deflate. However, in the photos, the nem looks fine.