Why are my daffodil leaves going yellow and dying off ?

[Marthaclematis]

My daffs which are at the back of the garden are blooming lovely but some of the leaves are going yellow and dying off - the flowers are still fresh? That part of the garden is semi-shade woodland but does get a good burst of sun for about three hours. Its clay and a bit compacted. Should i water them ? Feed them ? I've never seen this problem with daffs before. Thanks.

[Marthaclematis]

I have looked this up on the bbc and read...

"Premature yellowing of leaves and blistering on outer bulb scales: these symptoms are caused by nematodes"


I have used anti-slug nematoades watered in about 10 days ago... are they referring to them? Could they have caused the damage?