That looks a lot like my SSH did. Can you verify the roots are actually getting wet?
I thought mine were, but I was wrong. I discovered this by also removing all the clay pebbles so I could look. I ended up lowering my plant further in the net pot so the roots got water and that worked. But the simplest solution is to top feed that plant until it has roots long enough to be in the water. My guess is it is drying up. Check out my journal if you like: