what went wrong suggestions?

I bred my 3yo Blizzard to a proven charcoal het amel this year expecting a 50-50 hatch. This was the girl's first litter, all but one (so far) eggs are infertile. Tiny eggs with a hard yolk, any suggestions on what went wrong? Everyone knows me, and I am usually on the other side of the question. I am considering double-clutching her now but would like info on what may have gone wrong so it doesn't happen again. 14 infertile, 1 possible good egg. Also it has taken almost 48+ hours for the lay so far (looks like maybe 3 more eggs still to come). Thanks friends.
Reverend Sterling Kyle