Android works differently than Windows in that when an app is idle it shouldn't be using cpu (battery) even though it's showing up as RAM usage.
If your battery is draining faster than normal it could be, as stated above,a rogue app. It could also be a weaker than normal signal due to a cell acting up. and your phone is using more power trying to hold a signal.
I'd suggest also checking any apps you may have syncing data , especially any you've recently installed because that can be a battery hog as well. Things like weather apps can drain the battery faster than normal by syncing the latest weather data frequently. Apps using push notifications can also be a vampire to your battery as well so lower your sync schedules to the longest time period that works for you and see if that improves things.
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