EBJD fry

I had about 6 baby EBJD fry under 1/2", in a 5 gallon tank to grow out. Had a small filter cut back to keep flow from being to strong, they stayed in there for about a week before 5 of the 6 died and now the last one isn't looking to good. I did a water change about a day n half ago and all parameters are good, ph is about 7-7.2 and water is soft, 0 ammonia and 0 nitrate. Trying to figure out what happened, before some of them died they never acted weird but others would swim to corner and go vertical with head by edge of water, i didn't have a bubbler but the filter overflow dropped about 2-3 inches catching air and creating bubbles in the small tank. Anyone have any idas? or anyone raised fry to good size adults that could inform me on the water parameters you used? I talked to the place that I got them from and seems their water is much harder and higher pH, more like what african cichlids like? At this point I have no idea and am welcome to any advice, I would like to raise a few just to add their color to some of my bigger tanks.

Filter was from a cycled tank with no issues to date and I did 2 waterchanges in the week or so I have had them.
and I wouldnt say 0 per say, there was some color but not really enough to say 5ppm.
They were so small, I worried about them finding the food in a bigger tank.

EBJDxBGJD I would assume, bought them. That would be a question I need to ask, of course I believe they would have an idea that the EBJDxEBJD doesn't work..

Good thing I just picked up a 40 breeder! What size pump did you use on the 36v sterilizer?

So the slower the flow, the better it works, correct?