Seeds gone mouldy

Was the compost too damp ?

I had a similar problem this year raising vegetables in a greenhouse.   It arose because I was not differentiating between established plants which needed large quantities of water and plants yet to germinate which required water infrequently.   When I put them in different places and sowed the seeds in damp material underneath and dry material on top and watered only infrequently, the problem reduced.   But older seeds will tend to rot rather than germinate.