Using RO water does not necessarily have to mean zero hardness. That is why I was asking. Your RO is probably removing ions with overall efficacy around +-95% ( some membranes are a little better or worse + it depends on the pressure, temperature and so on) So dependent on the input, one may be getting RO water with 0,3° of alkalinity for example, which may not be measurable by simple DGH drop test, but may be suffiecient to harm the eggs. Of course, if you have some mixbed patron at the end of the system, or if you drop the water over bigger amount of peat, than it should remove the residual hardness. If there is any, lowering the pH even more could help too, there is usually a relation between these factors, so the higher the hardness and/or alkalinity, the lower pH may be needed for the eggs to develope. Of course there is some range of conditions where this is applicable.
I would worry about the litter at the latest. I would check the water first to be sure.