Cichlid behavior

I've had a cichlid tank now for 10 months. I faithfully maintain water
changes, salt buffer, algae control,etc. I have about 14 common cichlid
varieties in an established 55 gallon tank.
To this point, it has been a very harmonious tank, everyone seemingly
getting along, no strange behavior.
I have a pair of Acei that have recently started what I perceive to be,
mating behaviors. They seem to curl up, fins flipping rapidly, etc. However,
NOW it seems like everyone in the tank is performing that behavior
regardless of race, creed or color. Today, I found one of the Acei on the
floor. It had apparently leaped out from the only small open area around a
filter. Fish that were previous "out in the open" now seem to be hiding.
Can anyone shed some light on what is going on?

Thanks,
Greg B.