you cut too much off at once thus putting the plant under stress gradually
bring your height down spike scarify and feed if no rain about during the
summer keep well watered.

Two to three inches tall for a nice springy turf. Shave it lower and it
becomes susceptible to all sorts of nasties.Maybe trim for a striped effect
in midsummer but generally leave it longer than most people mow.
Cut very low and you will destroy butterfly larva that live on the ground
during daytime but feed at the top of grass stems during the evening (think
it's the brimstone).
The starlings are busy on our little patch at present- heads to the side
listening then a quick dash and deep probe to drag out the grubs that love
to eat grass roots- crane fly larvae, otherwise known as leatherjackets. The
birds do a good job as you would otherwise have to use wormkiller to see
them off.
DaveK.