A quick update. Still have all 6, and they are slow growers.
Tank has been cool for the winter, sitting at 64 - 66F, though appetites have been alright. One eats everything, and has grown and thickened up more than the others. "He" has a wide head and high dorsal fin, and I suspect is a male.
There is another, smaller one that does not have the wide head or girth of this one, but has a bright blue dorsal fin.
Several have a bit more red on their flanks, which I'm suspecting are females. None have grown beyond 4", and there is only a little posturing aggression, so perhaps they need more time before they show sexual differences.
This one likes to hang out in the java moss.......O