Dark interveins on leaves

Hey happy growing! I noticed your plant has some of my plants issues as well! I am still new so take what I say with a grain of salt but it looks like a nitrogen toxicity a bit as well. The curling inward and down leaves and dark leaves are the tell. Try feeding less or running a clear the watering in between feeds helps

It depends what medium you have your plants in to be able to plan effectively however brown spots are usually occur from a few different reasons may it be underwatering or overwatering among others reasons such as nutrient deficiency or low light. I personally noticed it on two leaves of my plant, likely from a late watering. I saw it more on a hydroponic grow I tried and the brown spots were uncontrollable.

Yo la alimentaría con cal-mag en una dosis un poquito mayor! Nada de que preocuparse!

I'm with herbaledu on this one, nothing to worry about. She is probably getting used to the light strength. Keep going, doing what your doing and you will be fine. Also because your running in soil try and do a feed water feed water feed water during the grow so you don't get salt build ups in the medium.

Nothing to worry about imho. Happy growing