I'd turn off all your 3rd party apps and see what happens. Also you said you use workout. I've read a lot of people saying the work out apps kill the battery. That stinks.
My own experiences with this; I always end the day with 40-50% left. One day I had it track an outdoor cycle ride for 2 1/2 hours. I ended the day with 13% because of it. So... No more excercising for me...I don't want to kill the battery!!!! Lol just kidding. But it is a shame that the workout apps put so much strain on the battery life.
I too always end the day with 40-50% left, I am having no battery issues.