Even through the blurple i recognize this....you say losing leaves from the bottom up?
Before your start chasing yourself around in circles looking for pH problems and nutrient problems and flushing and on and on... I'll ask one question:
Do your girls have a source of fresh air coming in?
I'm going to guess that you don't. I'm also going to guess is that you've seen signs of this a long while ago and it has been getting worse ever since. Snowballing.
The plant is eating itself looking for CO2. I can show you pictures of what happens in the advanced stages of this.