iPhone 4S draining battery faster than it's charging

So, I, like others, have had issues with my iPhone ever since upgrading to iPhone 6.1. I went to an Apple store, and because the connector dock was acting strange they said it might be a hardware issue. My phone basically bricked after that, and was dead for 2 days, but for some reason I kept it plugged in, and out of nowhere I had enough charge to restore it (via iTunes, using the restore method rather than a simple restore). After that it charged to 100%, just like normal. I went back to the Apple store, they tested the battery and said it was running perfectly. I asked if I can start putting apps and stuff back on, they said yes, I did, and now it doesn't charge past 70%. I restored it once again, and now it won't charge past 65%.

Can I blame this on 6.1, 6.1.1, and 6.1.2? or is there something I should do that might fix this? I've used multiple cords and chargers.