Spacebucket grow - Northern Lights

Germinated Nirvana Northern Lights fem in paper towel, then transplanted to Jiffy pellet, then placed in solo cup. Currently using 80/20 coco coir/perlite. No nutrients at all yet. Watered around 40mL tap water (pH 5.9-6.2) up until 4V, then realised I was over watering so no water since. Around 5V, I started to think there was some leaf discolouration (dark leaf creases and veins and pale elsewhere). I’m not worried about it, I think it’s probably nothing to worry about. Thought the growth rate had stalled a bit around 6V, but then checked out some grow diaries for the same strain and realised she looks right on track. Looking gorgeous so far.