I'm assuming you are talking about the curled up edges.....have you lowered your light recently? If you want you can simply dilute the total ppm back.....doesn't sound to me like you need to totally flush the system. If that's a 0.5 conversion rate....I'd probably try to lower it about 100 -150ppm and keep a close eye on ph. If they are nuteburned you will usually see the ph rise more quickly and more often.