They're very easy to revitalise.
Probably a combination of poor soil and underwatering. I'd dig a ring arround them at the end of summer, remove all rocks and stones, add some homemade compost and watch them thrive next year.
I'm in SE6 and have about 8 ready to be rehomed (in pots grown from cuttings in the great strong air of the South Circular) and you'd be welcome to some if you decide replacement is what you want.
They're very easy to revitalise.
Probably a combination of poor soil and underwatering. I'd dig a ring arround them at the end of summer, remove all rocks and stones, add some homemade compost and watch them thrive next year.