Having issues closing out rounds

I've been planing disc golf off and on for about 30 years now. Up until recently I didn't devote much time to the game, but the last few years I've been getting games in at least one time a week. This has really helped with my score and it's been trending down nicely. Still don't regularly break 300 feet on drives but getting there. However, now that my score has started to stabilized I noticed that my accuracy and distance seem to drop off after about 12 holes played.

My home course is a par 3 course at around 5200 feet. I've pared every hole with the exception of a rather difficult uphill hole but will usually get a bogey on it. Based on how we play the course we sometimes start on hole 13 or hole 1. Both times it seems after around hole 12 I just seem to fall off a bit. It's not like my arm is tired or anything, it's just for some reason I'm not as accurate.

Anyone have any suggestions on how to ensure that I'm able to finish the round strong? Any workouts that may help with conditioning or something?