Is this a plant from seed ? .it looks healthy the discoloration can be from a bug not mites but thrips can sometimes do that damage but that aside if you have no small worm like creatures on the underside of leaves.very small and difficult to see without a microscope sometimes.this could just be growing pains or genetics of this plant .check for bugs that aside just feed and move on .it may outgrow it or not but shouldn't affect the outcome .not a deficieny from what I see.try a pinch of Epson salt in water like 1/4 teaspoon in a litre of water and water it in .should green up those leaves from magnesium.and make sure your using calmag with your food to help the plant uptake food.i ph at 6.5 in my food for soil feeding 7.5 May be a little high 7.0 might be better .30 years of experience in case you were wondering .still learning .have a good one and good luck.
