I am in soil, and as another member just mentioned the soil does have quite a bit of woody mulch in it which might be consuming N as it breaks down?
No soil amendments
The manufacturer has a feed rate sheet somewhere which includes soil, I checked it out as I used to grow in straight coco and that sheet said coco nutes at half strength for soil. they also make an "elements" range which is just for hydro.
I have upped the nute strength by 50% and added 20% more N booster, PHd to 6.5 and done a huge feed this morning. also included H2O2 in the solution to see if it knocks down some of the bacteria which are making the N unavailable due to the composting action on the woody mulch component of the soil. If it all turns to custard I'll rip them all out and start fresh with pure coco. no dramas, I've got 6000 seeds left off the mother plant.
thanks heaps for your help.