"James Dawson" writes:
This years new growth has predominantly yellow leaves (with dark green
veins).
The trees are fed regularly with a citrus food.
What is the problem?

Probably needs a dose of salts. Epsom Salts. Disolve a few spoonsful in
a bucket of water and water around the plant's drip line.
--
John Savage (news address invalid; keep news replies in newsgroup)