What light are you using?
I use a 1000w HID/Hortilux HPS from Seedling-Flowering. I have the light no more than 24 inches from the top of the canopy. Often closer when theyre bigger, and especially in winter, when its easier to cool.
I also run a Gavita 1700e at 24 inches.
You may think about bringing your light down closer.
How bright is the sun in the Andes mountains, at the equator??? Get my drift?? Weed can take alot of light if you give it good ventilation. The sun is over 125w sq/ft at the equator, or higher at noon. Strong light, and a slight breeze from the start will negate weak stems. I like to see all my plants slightly moving. Weed needs good airflow to do its best.
Weed needs only a few things.
Strong Light
Proper food, and water
Good light growing medium/soil
Knowing when, and how much to water. Take most of the guessing out of it if using a peat base or similar by using a cheap Lowes/Wal mart Moisture/Light/PH meter, and dont let the needle go to dry line. Always low moist. Take several reading from different location in container. Also do the lifting the container method, so you can also learn to judge by the weight of the container. Ive used a Moisture Meter for 40 years. Takes all the guessing out of it.
Ventilation.. One cant stress how important proper ventilation, or climate control is. Get all the fresh air possible, when lights are both on, and off. I also keep fans on 24/7, even when lights go out. Plants use 02 when lights are out/Respire, and give off CO2, and use CO2 when lights on, and expel Oxygen.
If any area is compromised, you will not do as good as it could be.
