Yes they can revert back especially if they are not 100% converted. Larry Grace thinks one reason you may end up with a dip after a conversion has been done is that part of the crown didn't get the chemical to it and when the offshoot fans grow out they can be dip while the main fan remains tet. I read that heat, stress, and various other factors can cause it to convert back in the early stages of growth. That's why it can take years to convert some daylilies. Fred has waited 4-5 years for a conversion before.