Hi, thanks for the reply.
It's been filled for almost 3 months now.
I don't have a way to test my gh, but I do use a bit of gh booster with my water changes
and I'm using Thrive+, about 2 pumps per week, and the tank is about 8 gallons.
I suspected it was a Nitrogen deficiency early on, so I added some additional dry KNO3, but it didn't seem to help it.