Personall mate I don't think this is underfeeding rather a touch of to much feed?
With the bio-tabs now kicking in and the added liquid feed it does look like those leaves are getting burnt mate?
As I said in "The New" diary do you have anyway to measure your ph/e.c run-off and levels going in?
Kind regards
Mark..
I may have gone from one extreme to the other
Everything ph'd to 6 going in. I'll keep an eye on new growth, they're due just water next anyway