From memory your tank is see through so can be viewed from both sides? this might be spooking them a bit as well. They will be seeing movement / reflections from all angles, being that they are still small i would say these two factors could be whats causing them to hide. I agree with the others and add some more fish, prob hap or peacock as another mbuna won't help( they like the rocks).
I would def pass on the arautus, check out the net for all the horror stories of arautus killing all other tank mates, these guys get super aggro and need big num and a lot of space. I would look at a few male peacocks and/or haps. Or you may be able to have 1 breeding group of peacocks and 1 breeding group of haps.