Keep in mind I'm just a noob myself but those tight little leaves and the downward tips suggest a PH issue, perhaps too high. Do you have the means to check your ingoing and outcoming PH levels? Also I'd be thinking about watering amounts - is it too little, too much, a bit of runoff or just right. Heat and air quality consider as well.
Its probably just a little detail that needs tweeking - I'm hoping for you anyways