Nick Maclaren wrote:

Check over-watering, use of alkaline water and something eating the
roots. You are probably overfeeding it, too - citrus do fairly well
on benign neglect.

Once I went over to summer feed, I was getting some leaf drop,
especially on branches that bore fruit. I assume this is down to
over-watering. I didn't water until the top surface dried out, but it
looks like I will have to neglect the plant.

However, I have plenty leaf growth on newer branches.

Some brochures state that citrus should be watered every week in summer?
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