First grow

It's the second day of week 10 and I am trying to catch you all up on what's been happening. So far so good I have stopped all nutrition and just giving 6.6 ph water to the plants, I have noticed since doing this some of the leaves have started to change colour to a yellow/ brownish colour is this a good sign? I am also wondering when is the best time to start and change the light schedule so they are ready for harvest? Also this week I will be going away with work for 3 days it's a shame that they are not ready to harvest now, my neighbour will be watering them for me while I am away. My neighbour did a good job in watering my plants for me while I was away, they are looking good and plump I am hoping that week 12 will be the week I harvest my plants.