They are fairly tiny. If they are in a tank with other fish they may be getting eaten. I have 9 RCS with Kuhli loaches and have only seen 2 babies. One is growing a bit but the other one was only visible because it caught my attention swimming. Smaller than 1mm. I'm new to shrimp too so my knowledge is limited with them. Ialso have a female shrimp that developes a line on her back occasionally. I noticed it when it sat on top of my filter and thought that maybe it had dried out along the top, but it is still healthy now.