Hi catwoman ,
I don't keep either , but I do keep Cockatoo cichlids [Apistogramma cacatuiodes], they grow a little larger than Checkerboards [crenicara filametosa ] .That may be an old name
.
I also keep B. Badis Badis , they grow almost 2 times the size of Scarlets of which I had one male for a couple of months R.I.P.[ current to fast , I think ]
With these [ your ] fish I think the Ph should be no more than neutral down to 6.4 , maybe 6.7 as a good medium , temp high 70's -80 degrees , and the water on the soft side .
[ live] Plants will make fish look better IMO/E .
I think you have it right , water flow could have something to do with it[ what do you use ?] , as could not having a good number or retreats , caves , rocks , plants for them to relax around .
A few of the members here will say the more hiding places you have , the more you'll see them , from my experience this is true
.
I use both 3" and 1 and a 1/2" red clay flower pots in my tank [ I think 15 pots in all ].
Also 3 coconut shell halfs , and rocks stacked making even more crevaces , and a few plants as well [ the easier to keep types ] .
My fish get along very well .