iPhone 4s internet download speed super slow after iOS 7.1

I've been experiencing very slow download speed over wifi on my iPhone 4s and my iPad 2 after installing iOS 7.1 It's very frustrating because all other wireless enabled devices at home are working fine. My internet speed is 10Mbps download and my iPhone and iPad are only getting 0.01Mbps on average after iOS 7.1, which is really stupid. I've never experienced anything this frustrating with my iOS devices. Can anyone suggest a fix for this? I really need your help guys...