Why are you at 850 in week 3? Have you referenced the feed chart or any recommendations that CC has for using the UC?
Even if you choose to use H&G you shouldn't be running levels so high.
Also, your roots need to be touching the water at all times for the plants to hydrate. Have you hit up CC for tech support?
It seems confusing how you can have large plants in a dwc system but the roots have yet to touch the water. There are a variety of issues to address or you'll be struggling.
1) drop EC to CC recommendations for week 3 veg (0.6) or 300-350ppm
2) raise water level to contact roots
3) send the above post to cc and see what their tech support suggests
Post pics of your plants.