So are those black spots bug droppings on the leafs or they part of the leaf? Cause it looks like your plants are pulling a little more Potassium now that it is larger. Older leafs will yellow and die as the plant ages, but if those are black necrosis dots on the leafs then its lacking Potassium.
I noticed that you have filled at the EC or TDS section as 5-1-1. That is not a strength reading by a EC or a TDS meter, which measures the levels inside of your water mixtures. That is the N.P.K. on the plant food you are feeding or the ratios in the food. Find something with a little higher “K” around 3 to 6 will work for veg and add with your feeding. The higher the number though the less you need to add. Plus the added N wont hurt looks like your plant is maxing out its soil in the container.
If you grow plants outdoor make sure they have root space or start them later in the season so they do not tax the soil in their containers too heavy do not want them going root bound it can starve them of oxygen.