Grow Mediums Think Different - Very slow growth and yellowing

[teedeeree]

Hi guys,
I've mentioned this in the new growers section as part of my diary but thought I would ask here too.
setup
15 litre DWC buckets with lots of air.
400w LED light
RO water
silicon, calmag, rhizotonic, GH flora series nutes

This TD is 14 days from hatching and 13 days from being in it's dwc system, it did have a very stressful first few days due to my tap water being just awful but I have an RO system now.
It's been a very similar size for a good 3 or 4 days now and I can't see any roots coming out the bottom of the net pot (however there are plenty if i pluck a few clay pebbles off the top to look) the rockwool cube is pretty dry but not completely and I have been top feeding once a day with a mister.

To me it looks like it has an N deficiency, can anyone confirm or deny that looking at the photo? I've just done her a new res with more nutes (950ppm) and slightly biased towards the grow and micro components

Nute feed breakdown
-Full dose of rhizo
-Full dose of calmag
-Full dose of silicon
-3.5ml flora gro and micro hardwater, 1.5ml flora bloom (GH recommends 2.5,2.5,2.5 for seedlings up to 3 weeks old)

Any help?

 

[teedeeree]

Just to add, I'm 99% sure that the tap root has hit the res, temps in the tent go from 22 - 29 celsius in a typical 24 hours, humidity in the tent goes from 40% to 60% but I have had little humidity domes on the plants.
Ta!