What kind of deficiency is this?

a ph issue. but it is showing a potassium deficiency with the yellow necrotic brown spots but also a nitrogen deficiency and calcium deficiency. check your temps. you may need to turn your light down. this could be the yellowing and necrotic leaf spots. make sure your water is dechlorinated in one way or another. a simple and free option is boiling for 15 mins and cooling the water before use. chlorine toxicity can look like a calcium deficiency. also make sure you ph is below 7 for the best absorbtion of potassium at this stage. i add lemon juice because my tap is just barely too high and a couple drops to a gallon can get me close enough in the right range without having to check too often.