Plum tree - yellowing

[coachman]

One of my plum trees, is looking unhealthy.

The leaves have a yellow tinge.

Never seen 'silverleaf' yet, so I don't know what it looks like.

Any ideas, anyone.

[FB.]

I'd make a guess at the tree preparing to shed some leaves due to lack of water; it's been a hot, sunny and extremely dry year in my area - perhaps yours, too?
We've only had a couple of good days of rain since February. The ground is completely dry, down to 18 inches or more. The water butts have been empty for months and nearby (clay-subsoil) areas have earthquake-like cracks in the ground where it has dried and shrunk.

Apart from water shortage, it could be lack of nitrogen.

Silver leaf ought to turn the leaves silvery colour - hence the name - and cause dieback of shoots.