One of the poblems with using the bleach on those areas is that the bleaching will weaken the threads, and you will find it wearing faster in those areas. Also it will continue to bleach as you wash it each time in the future. I have discovered that buying fabric at Joann's, especially their flannel, is not the smartest thing I have done. I usually wash their flannel at least 2 times, sometimes 3 to get the excess dyes out, and to get it well pre-shrunk. Sadly, this is one of those "live-and-learn" lessons that we all have at one time or another.