Stems changing color

I think your plant needs better air circulation, less nitrogen and she will be happier than ever, don't worry about purple stems, it can be caused by a temperature.

Rah. Thats a very small amount of nutrition unless you preloaded the soil! Yeah get some nutes in there. I use super cheap hydrosol from Amazon. They send you pouches of the actual powder and you make your own bottles from it. It’s so much cheaper and I’m getting excellent results (for the most part - some plants are just dicks)

Nothing showing up on your leaves so the plant looks healthy this could be genetic. In the flowering stage when the plant focuses its energy on the buds red or purple steams are the sight of healthy development no need for concern btw you need to lower the EC a little by 0.2 you have burned tips 🍻

Could be genetic and/or lights. Hit with a little magnesium (Epsom salt) to see if it slows down or stops, but could just be genetics and environment.

Potash and magnesium is your two to worry. Increase those parts. Reduce nitrogen.

this is just unavoidable with LED... may not h appen with all plants but will happen. if oyu see it with all plants, it may be worth a little trial and error. If just on top, another sign it's nothing you can really do anything about. Whether it is LED or some other cause i don't know. Red petioles can come from low P. Low S causes red streaks in stems, not petioles. So, try boosting P, but it's never worked for me.