Agreed, you can’t fit anymore in there. Overcrowding results in bullying, which causes stress, which means sad chickens and no eggs.
You should aim for around 3 or 4 sqft per chicken in your coop (obviously the more room the better!). And 10sqft per in your run - your run sounds very spacious! I’d love an enclosed, covered run that size.
3x6 is only 18 square feet... I agree with all other posters that unless you are a super clean freak... and even then it would still be crowded, but flock dynamics can depend so heavily on individual demeanor. It's important to remember that when bad weather comes they may get testier with each other as others have mentioned. Post a pic of your set up if you want... ventilation is key to keeping moisture at bay as when they are closed up, just the amount from breathing can become quite a lot.
The more crowded they are, the more poop there is the more cleaning you need to do and also the more possibility of parasites and other illness spread.
Maybe consider getting rid of a couple older ladies next year and adding in some new ones so that your egg production will stay up next year instead of them all going into molt and leaving you with no eggs.
The 4 ft in coop and 10 ft in run is good minimum starting point for most average keepersto avoid issues caused by over crowding. BUT... it's okay to TRY what you are comfortable with and if it isn't working switch it up. I currently have an A frame coop that is only about 40 sq feet including the run... and I have 16 bantam cockerels, 3 standard cockerels, and 1 bantam rooster... that's 20 hormone raging idiots in a very tight space...
But they are pretty good boys as I cull for demeanor first and foremost.
Note that if you get a hen turn broody and occupy a box, it could be quite disruptive. Having a secondary kennel or enclosure to use if any quarantine or separation might be needed is always a bonus.
Sounds like you're already trying to solve chicken math, lol! Good luck!