Dead Frogspawn

Last year, we got 7 clumps of frogspawn in our pond (we made the year before) around spring time. We were very excited but then we noticed the 'blackdots' were not developing, soon they were going grey and all the frogspawn died. When we noticed something was'nt right we took some inside in a tank. We posted on other wildlife forums but got very little and inconclusive responses. We would like to know what is happening and why and can we do anything about it?

Thanks,

Ellie

:)