Tiger Barb not at his best

[Angus Child]

I have 3 tiger barbs in with a red tail shark, and two of them have picked up a "lean". they seem to swim fine but when they are stationary (most of the time) they lean, some times nearly 90 degrees, side ways and forwards, any one got an idea about what's wrong

 

[OldMan47]

Bump for a new member.