Hey bosscat,
Usually the yellowing of the lower leaves indicates it's hungry, but yours was showing signs of that before up potting. The new growth looks nice green and healthy. You're also feeding it nutrients now, so i would hold tight and carry on what you're doing.
As the plant gets bigger you need to up the nutrient strength.
@VetSmoke85 put up a chart, I'd look at that for guidance.
If you carry on feeding you'll be fine, but you've gotta let the soil dry out inbetween.
Do you have a way of measuring nutrient strength? I have a ec/ppm truncheon .