Hey 👋
Yeah, the little one doesn't look very healthy. According to your meter, both the pH and EC levels seem fine for the stage. Nevertheless, your leaves are suspiciously yellow (at least it seems that way in the pictures), which makes me suspect that you have a deep-rooted problem - at the roots! Unfortunately, this is the worst-case scenario with overwatering. Long story short: Try to let the soil dry out a bit in the hope that the leaves will perk up again. At the same time, I would recommend starting an alternative, as root rot is very hard to manage, if not impossible. I'm sorry.
I hope this helps, and good luck moving forward 👊🍀