Why? Why? Why?

Why does this happen to my washing?

I'm so fed up with it and I'm not even joking! My standards of housekeeping are low to say the least but I'm so annoyed that these weird bleached out bits appear every now and again on all sorts of stuff, t shirts, towels, and now these brand new pillowcases!

I'm not precious about stuff, but it really annoys me. Pillow cases are one thing but when its a top or something, and it gets a bleached out splodge right on the front, it's ruined. At the risk of sounding like a letter to Woman's Realm, I use non bio powder and gentle fabric softner, and other than washing everything in imported Alpine Rainwater and No More Tears Baby Shampoo, I can't think of anything less abrasive.

When I was a kid my Mum used to read Woman's Realm, and I used to think it was pronounced 'Woman's Re-lam'. She also used to buy 'Family Circle'. I expect they would have the answer I need!