Problem with draining battery on iPhone 4S

I have had my iPhone 4S since they were released last year. For no reason about 3 days ago the battery quickly starting draining fast. One morning I took it off and when I looked at the phone 4-5 hours later without using it once the battery was down to around 28%. I thought it was a fluke but the same thing happened yesterday and now the same thing today. Without even using it within hours the battery is almost dead.
I first did what I've learned is some type of reset by holding the home button down while turning the phone off and then turning it back on. I also have opened the task manager and closed all apps in the task manager. That is what I did last night but got the same results today.
I keep thinking there is some app that's running and draining memory or something to do with notifications. I have many apps on my phone and many are set up to give notifications but I have not changed much at all on my iPhone in the last 3 days. The only thing I can think of is maybe installing 2-3 new apps and one or so that had notifications. Why would it start doing this?

Is there any way that I can somehow find what app(s) or notification(s) are draining my battery or is it something else?
Is it possible that something is simply going wrong with the battery?

I've been fortunate to not have to deal with Apple support much at all. Is it something I can call them on the phone for support or is it best to simply visit a genius bar? The nearest Apple store is not that close to me so I was hoping this is something I'll find a solution to on these forums. As much as I'd love a nice new iPhone 5 this is still in warranty and I hope to have it fixed.

Thanks

If you have closed all apps as you say, then it's not possible for them to be running and draining your battery.

Such a severe loss sounds like a battery degradation issue, I would have Apple look at it. Calling them will just result in a very long process of re-troubleshooting the whole thing. One thing they will suggest that you may not have tried (and should) is to reset the iPhone (after a backup OF COURSE) to factor specs and see if the problem disappears.

Try turning off all location services, and do you have a good cellular connection? i have this issue when i have a low signal.

I'm going to try both of the above suggestions, turning of location services and also doing a backup and resetting the phone. Assuming that does not work I'll be making a trip to the Apple store. If they replace my iPhone is it possible they'll replace it with the iPhone 5? I would imagine I'll get another 4S which is fine but I'm wondering if they would even give me the option of upgrading to the iPhone 5 for possibly a small fee. It seems it just may be a good time to upgrade to the iPhone 5. Then again if I push for that they may suspect something with the timing of this problem. I've tried to reset it multiple times though and still today on day 4 it's continuing to lose battery power quickly.