Hey there Heisenbud, so growth rate is determined by genetics and Vapor Pressure Deficit (VPD). Genetics is genetics , maybe you got a phenotype that's just like that, nothing you can do about that. The other thing is something more controllable. So basically even within a grow box there are micro climates, it's not as even as we think it is, which i did find surprising when i started to measure it . Vapor Pressure deficit is the relationship between humidity and temperature , so it's affected by the micro climate based on your temperature and humidity you're not in the optimal range, you should be around 25°C for that humidity ... seems like a small change, but clearly over time it does matter. Learn more about VPD here : http://pulsegrow.com/vpd Hope this helps ! 🚀