Yes they will droop for a couple of days, when I flushed my mess a time back Dr. Greenthumb told me to use all purpose 10-10-10 fertilizer (Vigoro like product) at 1/4 to 1/2 strength on my last gallon of the flush. These were in Pro Mix with no amendments though. Your medium has nutrients in it so I'm not sure if you want to add any in during the flush, it seems like your just recreating the initial problem all over. I would kind of like to see if the flush fixed the problem first. Maybe someone else could chime in on this one to add some insight.