it is a high death rate but it does happen, more commonly with albino and related morphs.
The reason you are not finding any bodies is that they are being eaten by the other fish. This is quite often how the mortality rate can be sustained so high. High protein levels from eating too much meat, or illness being passed from on fish to the other. This is why daily water changes become so important, if a fry dies it needs to be removed ASAP!!!
More details as Jim said will help with IDing the original issue.
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