If I had to pick a favorite nutrient deficiency, it’s probably nitrogen simply because it seems the easiest to diagnose. That’s a lie; I love the way nitrogen affects the plant’s overall color because I find it gives great insight into how the plant is handling her overall nutrient amount.
It’s one of those ways experience growers can judge a plant’s health just by looking.
If you have a plant that is dark green, especially in veg, you’re most likely giving it too much veg nutrients which are highest in nitrogen and burn tips will shortly follow if continued. An overall pale green color is most likely a lack of nitrogen, but you’ll want to confirm by looking at your bottom leaves to see if they are yellowing or dying. Nitrogen is mobile and when your plant doesn’t have enough of it, she prioritizes the nutrient for the top leaves that are getting light.