It only takes a couple of days for white cloud eggs to hatch, so the fry very well could be theirs. I guess you could try powdered flake, but I have a feeling that's going to be too big for them to eat. I'm not really familiar with how one cares for white cloud fry, but infurosia might be a good choice? If you've got any live plants those tend to foster infurosia, as does green water.