it does not matter about seeds sprouting at different times as the plants will grow at different rates anyway its called
uniform growth and there are easy ways to sort that so no matter what height each plant is you can make the canopy even.
and i know what seeds are viable before i plant them(60+seeds planted and no duds).
when you know what you are doing its quite easy.
Uniform Growth
The light intensity from artificial lights drops dramatically as the distance from the light source increases. When the plants are not of equal height, the shorter ones receive less light and consequently grow slower than the taller ones. This compounds the situation and, left to themselves, the shorter plants will stop growing and eventually die from lack of light.
It is important to keep all of the plants close to the lights. This encourages stocky, full growth and can make the difference between harvesting stems and harvesting smoking material.
One way to deal with uneven height is to line the plants up to the line of the plant tops. As the plants grow, move them to different spots in the garden to accommodate their different sizes. Or raise the shorter plants up to the lights by placing them on milk crates, tin cans, bricks, etc.
The quality and quantity of light emitted by a fluorescent is strongest in the middle and weaker toward the ends of the tube. Female plants require more light than males. Once the genders of the plants become clear, move the males to the ends of the system, thus leaving the stronger middle light for the females.
LUDACRIS.