Got my Apple Watch 4 a few months back. Usually use it every day, all day and recharge at night when I get home from work. Some days it lasts all day (8a -5p) and it will be at about 70% battery. Other days it goes from 51% to dead from 2-4p. Like today – totally dead when I got home from work. I don't "use" it during work, but I might remove some notifications during the day. I keep it in theater mode and remain silent while at work, so it won't turn on and off unless I touch the screen. Is this just a strangely normal thing, or can something be wrong with my battery?