Botia Almorhae acting odd

Have had three of these guys in a community tank for 2 or so years when
they were juveniles, so they're about 2 years old. Moved 3 and 1/2
weeks ago (6 blocks). Tonight two of them (the larger two) changed
colour from their normally distinct black & white patterns to a greyish
colour with a much faded pattern. They have taken on this colouration
in the past when frightened, but have not done this a very long time.
The two of them essentially circled each other continuously for 15 or 20
minutes, nipping at each other's mid-sections and undersides - mostly at
the back half of the fish. This is previously unknown behaviour to me.
They normally just play "chase".
My only guess is it's breeding behaviour as described at:
http://www.loaches.com/breeding.html.
However this particular article didn't confirm if it was indeed breeding.