Bleach is a disinfectant not a particularly good detergent ...different animal...we used to use it in our industry but it has largely been replaced by products such as proxitane which is less problematic to use.
All I would suggest is get a small piece of polished f/g and leave it overnight in say 50:50 bleach....soon see what happens to the gelcoat in a more severe test,than how you are using it.