So I have had problems for the last year consistently getting good rates of success. About a year ago I switched from pure blend to sensi gro to raw salts 4 months ago till now. I didn't have to worry much about runoff or salt buildup with pbp. Then I start getting all these random problems. Clones not rooting, nutrient burn/buildup , slow growth etc. I have attributed my problems to salt build up and now have been watering to 20-30% runoff at ec 1.0-1.8 with ro water in promix I have been reusing (more likely compounding my problems). it has been about two weeks now of runoff after flushing everything with 300ppm. I took my last cuts a week and they did horrible again. I'm hoping the mothers were not fully back on track and just needed more time before cloning. Everything has 500-1000 ppm run off now and before I took my last clones. so my main question is what am I doing to keep my clones from rooting.

Here is my process: first soak rokwol cubes in 2-400 ppm flower food at 5.5-5.8 pH an hour or overnight depending. cut stems with clean scissors and stick in to ro water for 15mins to 2 days. Sometimes if left overnight the stems go soggy and shrivel up at this point even though they were clearly in water the whole time. The most locked out plants did this i believe.
Then I use clonex as I always have clean fresh razor cut under ro water. Then under dome in to rokwol cubes with heat mat and two t5 2' sitting on the top of the dome in a room of the house separate from my grow room.
From here I take the dome off daily to air them out for the first week and by this time most of them have died. the stems become soggy, shrivel up even though the top looks fine. They sometimes wilt wether I close then holes on dome or leave it off. This last time they had Alot of stems in the cubes that rotted or lose the outside layer and get mushy. I am ruling out lo moisture, high moisture, temps, cleanliness I think. This is absolutely killing me right now! I''ve taken literally 1000s of cuts only to receive a handful. I've tried so many ways its ridiculous. Read alot of threads and still not sure. All I can think is the salt buildup all this time is screwing me over. The only thing consistent thru the gardens is the salt. Any insight would be greatly appreciated. I have so many varieties I haven't ran and ones to don't want to lose. Really hope someone can help. Thanks farm.