Seahorse acting weird.

[Chooki11]

I have 2 seahorse in my tank, they have been in the tank for 6ish months now. They are both starting to swim upside down bang into things more and doing loop de loops, sometimes the one goes right to the surface and sits there on its side (I've thought it was dead a few times, it was breathing and swims around when I get close to the tank). Is this normal or is something happening I'm not seeing?
Thanks for any info!