Critical Purple: Leaves slightly yellow.

You have answered your own question.............minimal nutrients! Hydro/DWC or systems like those require you to provide everything. Skimping on nutrients results in plants not growing properly, i.e. turning yellow after only 2 sets of leaves.

Give her some Nitrogen and check the PH. No problem after that. And it will be a one and done fix. As N deficiency can be fixed in one watering.

For a plant this age and size, it's highly unlikely to be an underfeeding issue lol. Considering you're using drip feed irrigation and your hydroton looks soaked, the base of your plant is probably staying too moist. I'd let it dry out a bit. I personally never understood the need/popularity for a drip ring in DWC. An aggressive bubble in your reservoir will adequately mist your net pot enough to encourage roots to emerge.

Hello my friend, the cause for the yellow leaves is because of the wrong nutrient solution. There are 2 options here. Number 1 is not enough (or wrong) nutrients with not enough Nitrogen. Number 2 is the wrong pH value not within the range from pH 5.8 - 6.2