Not sure i totally agree here Robert. The colour of light does matter as leaning towards the yellow spectrum ( 5-8K ) calvin of light is generally better in aiding photosynthesis for plants.
So aim for a 6700K bulb at minimum of 2wpg.
I have 3.5 wpg
but still getting the issues with red stem plants. I find the main problem is when I trim and replant them they go through a short stack of shock and shed a few leaves and the odd stem might start to rot a little. After this phase they start to grow fantastically.
Always seems to happen after I repot them and its not a light/fert/co2
issu as i have 3.5wpg with EI dosing and 30ppm co2