Thanks cult. I noticed some downward leaf curling and signs of poor health with my Cinderella 99, so after the res had been in for about 2 days, I changed the water/ feed. Flushed 1L of ph water through it and seems to be recovering well.
It's canna pk13/14, it recommends 15ml/10L at week 5, though I've noticed a P deficiency with my last 2 grows so have been supplementing 0.5ml/L throughout and it's been beneficial.