So is it better to water at start of light time or...

It doesn't matter if it's day or night when your watering the root zone. But only water when it's really needed. Since you have excellent access to your pot you shouldn't have any issues getting leaves wet with nutrient rich water and the light causing any type of burn spots on the leaves. Afghan Kush is a mildew resistant land race strain. Humidity will fluctuate between waterings. Your at a point in your grow where the plant is stretching which is normal it will allow plenty of light/air circulation around your buds. As far as inter node spacing genetics, excess nitrogen,low intensity lights, day/night temperature difference of more than 10 degrees all influence this aspect. You can start to remove fan leaves from the lower 1/3 of your plant and remove tiny bud sites also which will never get enough light to produce much. This will re- direct energy to the upper buds. Good luck your going to have some nice smelly,sticky Afghani nuggets when your done.