What could cause my middle acan to close up?

[Zeal]

Weirdest thing has been happening recently.

Recently have been having this weird issue that this acan randomly closes up. All 3 have been next to each other since a August. Haven’t changed anything and just now this last month I noticed it’s closing up and randomly fully
Opening

The fully open picture was Sunday

 

[DSC reef]

It's typical behavior for acans to do this, inflate and deflate. It doesn't mean there's an issue or that the others should do it, they just do. I wouldn't worry at all as they look very healthy.

 

[Zeal]

It's typical behavior for acans to do this, inflate and deflate. It doesn't mean there's an issue or that the others should do it, they just do. I wouldn't worry at all as they look very healthy.

But just this particular one? Just worried they there might be a problem. Sometimes the far right one also deflates

And they’re not stinging each other because they open up regularly

 

[DSC reef]

I would see it all the time. It's weird but nothing to worry about IMO

 

[Zeal]

I would see it all the time. It's weird but nothing to worry about IMO

Alright, anything I should look out for just incase?

 

[DSC reef]

Could be an invert crawling on it but looking at them, they look really healthy. It's just normal behavior, even our trachyphyllia would do the same.