yea dude those roots are not normal...i have no clue why no one told you this before.. That gunk is whats screwing you up those roots deffinatly have the beggining stages of rot...
Here is how to remedy your ladies...
step 1. take plants out one by one cut off the bottom slimey gunky roots off with scissors, these roots are dead, trying to treat this gunk rot will not work and you risk recontaminating the system even after you change your water out..
step 2. one by one dip the rest of the remaining roots into 3% h2o2 (buy at local drug store) for about 3-5 seconds, you will notice bubbling when u dip into the h2o2 this is what happens when the h2o2 kills off everything bad on your roots....
step 3. 10 seconds after dipping in the h2o2 dip the roots in regular tap water..
step 4. repeat step 3 and step 4 until their is no more bubbling on your roots.. usually 3-5 times, h2o2/water/h2o2/water/h2o2/water ect.... after doing this DO NOT place back in the UC.. Set them up into a bath tub or anything you can put a little water in...
step 5. Drain/clean/scrub UC i like to use physan20 inbetween runs...
step 6. Refill with fresh water and Capulators Bennie Tea (ogbiowar) root pack and foliar pack OR
Cultured Solutions Roots... One or the other DO NOT USE BOTH TOGETHER...
step 7. Before re entering the system do step 3-4 one more time to be sure no bad shit will get into your system..
step 8. Keep it simple quit putting all the bullshit in your water...
Cultured solutions A+B one bloom booster and your choice of root zone conditioner THAT IS ALL...
Dont over think things, keep your PH between 5.8-6.4 your ppms between 180-450 (in veg) your water temp between 64-68... Dont look at your roots every 10hrs... let them chill and do their thing... Follow these directions and it should get you back on track within 1.5-2weeks
One last thing, if you are using rockwool or any other type of media that retains water make sure your UC water level is BELOW the UC net pot... Dont worry about roots not getting water, the humidity inside the bucket is 100% RH, humid enough to make roots grow down into the water..
I hope this helps u bro