Clowns rushing around madly

We left the tank at 5pm yesterday, fed the fish immediately before
leaving, got back at 7pm today (26 hours later), essentially having
skipped a feed (normally feed twice er day). Lights were on timer.

Fish all looked normal, fed them, then one of the clowns started
rushing around the tank madly (not seen this before). The other clown
started following. Other fish behaving normally, inverts all look OK.
Ammonia, Nitrite, Nitrate all zero. SG had drifted up a bit to 1.022.

Clowns still rushing 2.5 hours later (though slowed a bit).

Ideas?