What are these fishes and why they spend the whole time on the surface.

[duanes]

Duanes
I didn’t quarantine them, so Does it mean it is already too late to remove them in case if any of them have any lethal disease. How would I know if anyone would be sick? I don’t want to risk any disease in my tank.

You might as well leave them in now, if (Doesn't mean they were) infected bacteria, viruses, even protozoa can be immediately shed (or not).
And Deadeye, the cichlids in the video are a few Rocio (jack dempseys), if I remember right they were @ 10-12", and the largest shoal, are Mayaheros uropthalmus.