I'm currently going through Barney's Farm catalog, Cali strains - Do Si Dos 33 wasn't a great success for me, but Blue Gelato 41, Biscotti Mintz and Orange Sherbert were excellent, just started a Watermelon Zkittlez 2 days back. :D:D:D
I agree with Markshomegrown;
- feed half strength Nitrogen nuts and have a look at what your CaMg feed is as it looks a little low to me from the blemishes on the leaves.
- I would also mix a straight water 5 liters of PH 6.0 and pour it through your medium and collect some run-off to check...