My ruby shark is acting wierd?

[Sharklover]

Normally it is pretty "quiet" and docile,hiding somewere but now its just rolling on my gravel , it swims upside down then goes right for a sec the back upside down any clues its about 1-2 months old in a 37g with 2 balla sharks a red platy a bristle nose pleco and some blue/yellow fast fish thing but they all seem fine and they are all around 4-5 months older than the ruby also they have never picked on it and there is no ich any clues guys?(ps- i no its too small just answer the question and dont say its dying cuz the tanks too small cuz hees the smallest fish)

 

[Mogurako]

What size of tank? Type of filtration? Water temperature? Water parameters?

 

[Mogurako]

EDIT: never mind saw the tank size, can you take pictures of the shark?