I've got this mature Daphne - sorry, I don't know the name but it has dark green leaves with yellow edges. It's about 4'H x 3'W. I've had it for several years. It obviously likes its position - right in front of an east-facing wall which gets the morning sun till about midday - and must like the general soil conditions which are pretty claggy/clay.

I've had an excellent display of flowers this year but some of the leaves have gone quite yellow and look very poorly! The shrub obviously is deficient in something but I don't know enough about gardening to be able to say what. Can anybody advise me?

Thanks