White Widow - My First Grow

Sticking to a 4L every 2 day watering schedule. I get a little more than 10% run off. Also sticking to 4x4 on the grow and bloom nutes as per the biobizz schedule for light mix. Yellowing of leaves appears to have stopped however a sister plan in a smaller pot appears to be still suffering, although that's most likely down to pot size and how many nutes the medium can hold. Tempted to try +1ml/L more bloom nutes next watering. Water going in has been PH'd to 6.8 as the run off was 6 which was a little concerning. I'll continue to monitor and adjust. QB@150W