Clown swims with nose in the air

We have just introduced 2 young tank bred Percula Clowns into a newly
cycled tank. They looked fine in the LFS, but when they were put into
the larger tank, we noticed that one of them swims with its nose in
the air - almost like its default orientation in the water is at a 30%
angle. This is noticeable when it is resting/stationary or swimming on
a straight horizontal.

Apart form this it appears to be fine. There is no tilt in its
orientation (i.e. viewed from the front, it swims perfectly upright)
and it has no problems with manoeverability or stability in general.
It is able to target food particles very precisely, for example. It
therefore doesn't suffer from the more classic swim bladder related
symptoms.

The LFS says they haven't heard of this before so it could be the
stress of transferring him home and into the new tank and that he
should settle.

Anyone recognise this kind of behaviour or have any advice?