I transplant from the solo cups to 2 gallon pots at 2 weeks from sprout.
Don't go by time though......go by size.
15 days from sprout......... the day after transplant.
I can't help with the light question but the cold temperature will definitely slow growth.
You might consider starting in smaller pots next time.......I start in solo cups.
My tap water is around 200 ppm. Obviously there's a problem with the chart you're following because you started this thread due to developing issues with your plants. You ask for help, yet rather than take it you question it.
Good luck to you!