Portuguese Laurel HELP!

Good afternoon....I have two Portuguese Laurel trees in my back garden and I'm worried they may be diseased or dying. I attach some photos of the leaves as they started turning yellow (the odd one) a few months ago, but a large number are now starting to really turn yellow. Not sure, as I say, this is a problem or if it's natural? TIA

 

Take a deep breath and relax....

This is normal. I've a number of well established laurels - all have some yellow leave. Laurels are evergreen but do lose some leaves.

 

Thank you so much for the reply. Phew.....Just one more question (maybe two) if I may. When is the best time to prune them back? and What feed do you use and how often? Thanks.