Hello. Welcome back!
I have CL
's and they are really wonderful, but odd fish.
Previously I had changed tanks and the fish literally disappeared for weeks and I thought they had died and I just didn't see their bodies????!
But they dug a cave in between some stones which had a big DW on top! How they all could fit in there I really do not know.
One day, when I was feeding the other fish, one larger one popped out and really startled me since I thought they were gone!
So all that to say perhaps they are getting used to the tank.
What substrate came from the Oscar tank? What are the pH, GH
Maybe the water from that is different than before.
They really love caves and rooty DW and will use dense plants to hide.