Another Puncture. What is Going On???

Had another puncture, 2nd in a month,  rear wheel this time.  What is happening - I have had no punctures in years and years of cycling over thousands of miles and now 2 in the same month. Can't believe it, anyway I am getting new tyres for America, Foldable Marathon Supreme 700x28. Any comments on these tyres welcome.  Still, this is great practice for me and I managed to change the back tyre (slowly).  Only problem I have is closing the QR lever but that is a matter of strength and correct tension.  Will have to work on it or ask a passing friendly redneck!!