Have you checked for Ammonia, NitrIte and NitrAte?
Possibly not a cycled tank.
Those are all community fish and shouldn't get stressed by a reflection of more of themselves.
Maybe add some long plants around the mirror area to add cover of it and see if they start swimming around the rest of the tank.
Are you familiar with the nitrification cycle? Have the fish and tank only been up and running for a month? If so, it is possible there are some water parameter issues?
What size is the tank?
How often are you doing water changes and how much?
What is your filtration?
I would do a couple 30% pwc
Test first and see what the parameters are. If you do not have a test kit then save a cup of water can be in a ziplock bag or rinsed and clean jar. To take to the local fish store.
After the 2 - 30% back to back/one right after the other check see if they seem calmer and stop staying at the top part of the tank as much.
Frequently they are agitated and act up when their water parameters leave the safe zone and become dangerous to them.