Most likely drought,as you're in the south - our front lawn looks like the sahara desert here in west London, and that's not too far from you.

Dear Bamboo. Thanks. We try watering but our ground drains well. We will give extra water and hope for the best. Thanks again. Philippa

Remember also that the older leaves (you do say elderly Ceanothus leaves) turn yellow and drop out at this time of year too Philippa.

Just to add, Philippa, on the assumption you've had as much rain there as we have here, your lawn must be looking like ours - this weekend its turned into a brownish yellow dustbowl. I sense a hosepipe ban coming on....