Please can anybody suggest why this problem is occurring

I have only a small lawn about 3 sq yards but I have been experiencing major problems for 25 yrs the lawn tends to die off around the edges where bald patches appear. and small bald patches appear all over in time. I have recently dug up the old lawn and turned the soil over at least 9" deep. I have laid new turfs which were good quality at least 2" depth but already after just 6-8 weeks I have notice bald patches appearing around the edges it is driving me mad . We have no pets, I water it regular about every 2-3 days and the only food I have been using is a dosage of miracle grow. Somebody suggested that this has only been happening since I bought a new flymo which I used on the old lawn and the new but feel this seems unlikley.

I would be grateful for any suggestions or a solution to this problem. regards jem lawn