Why so small?

Thanks all, I'll try and amend and go photo next grow

It could be possible that there is not enough available nutrients in the soil for the plant to thrive. You could try to add a nutrient tea when watering and see if that helps the growth.

90w light, ruderalis, no ph regulation I guess is normal. less light= less photosintetic activity, less nutrients uptake. PH= less root growth and nutrient uptake if you're too far from the optimal range. Ruderalis= paired with low light source is going to produce small plants.

I'd say its not enough light 90w leds won't give much out so I'd get a better light for better results happy growing

@BastardGrower Auto's are notorious for the occasional runt even with the best setups this can still happen . just try to adhere to the basics and it will grow as it wants to , unfortunately not a lot can be done to speed it up