How long have you had these fish? Have you tried keeping the lights off for a day or two, and just letting the tank be lit with ambient room light?
From my experience - fish that like to hide are just not used to their new surroundings and/or don't feel they have "safety in numbers" (too few of their own kind).
From my experience - fish that like to hide are just not used to their new surroundings and/or don't feel they have "safety in numbers" (too few of their own kind).