Dig them up, spread them out and feed them. Check both Daffs and Snowdrops for Narcissus root fly.

Thanks OB. I do feed the daffs later on but never sure when to do it. Is it six weeks when they begin or finish flowering? I've never fed snowdrops but will do now as you suggest. Can you advise me on what type of feed?

This happened to my daffs one year and plain old Miracle Gro sprayed on when the flowers had died but the leaves still good was very effective.

Best time to feed is as Steragram says, after flowers have finished, but while the leaves are still present. Any foliage feed type stuff will do.
Then when they have died down naturally you may dig up the bulbs, split them up and replant a little deeper than they are in the ground now. I would put a little (and that means a little not a great big handful) of Bonemeal under them too.

Thankyou Stera and Owdboggyy? I'll do as you suggest once the snow and frezzing temps have retreated. Mammoth task though - got snowdrops and daffodils galore.