Cloudy nipples!

The bottle nipples start out clear and shiny, but turn cloudy and hazy. I wash them with babyganics, but have also tried dawn to see if that gets them cleaner. They also get a wash and sanitize every other day in the dishwasher. I replace them every month and a half to two months. I use como Tomo bottles if that makes any difference.

Any tips or tricks to keep them looking clean?