Hi guys, I had my garden turfed four years ago and these light patches have started to appear.

Can anybody identify them and suggest a remedy or method to get rid of them and bring my nice green grass back?

I also have one dark patch, which almost look water logged! The photos of this follow the light patch photos.

The only maintennance the lawn has is treatment by Green Thumb four or five times per year.

Any suggestions you can make would be very helpful to me!

http://imageshack.com/a/img545/219/eptg.jpg

http://imageshack.com/a/img41/2016/06gv.jpg

http://imageshack.com/a/img560/2091/yhca.jpg

http://imageshack.com/a/img46/7617/owmk.jpg

http://imageshack.com/a/img585/8568/ri6s.jpg

http://imageshack.com/a/img850/4899/sot9.jpg