What EC are you applying? With drip (especially at only 3 times per day), EC levels in the media will rise. Despite what people say, hydroton rocks are porous and do retain salt. I'd advise you to increase drip to at least 4-6 times during lights on, and have one at least 30 minutes after light turns on. Droop prior to lights out is normal, although in your case it seems a little excessive. If your humidity is low, it could be resulting in the plant transpiring too much water and shutting down photosynthesis in favor of "sweating." Most indoor grow rooms experience this to some degree. How high do you have your light? Don't keep a 400 watt any closer then 8 inches. Your leaves look fine, stems look a little soft. You should try upping the potassium a bit or adding supplemental silica to your grow. With the hydroton though you can pretty much keep almost continuous water, as long as its recirculated and oxygenated. So up the drip frequency to i'd say 6 times per day at least. Water farm buckets are just like yours except constantly dripping. The roots coming out the bottom- there's nothing you can do about that except make sure you're supplying adequate water and nutrients. It may become a problem if your lady gets root bound when transistioning to flower. I don't know a lot of people seem to think hydro is simple but I found there are a shit ton of factors you have to consider and balance. I've been doing it for a while now and I still am learning every day. But she looks good though.