Is the iOS 7.0 update making my internet slow or is it the server?

Ever since my sister and cousin updated their iPhones to the iOS 7.0 update our home internet has slowed down. Video's used to load reasonably good and now we can't even watch the intro to a video. And when we open a new tab the longest I've had to wait for it to fully load was at least 5 minutes. This has been going on for 4 or 5 days. This has happened in the past but when I tried to fix it like I did back then it didn't make any changes. I use Firefox and have tried using Google Chrome and Internet Explorer but the problem still insists. I even tried using my phone but nothing will load.

For anyone who would like to know I have a Black Netgear Optus Wireless modem.

It would really help me out because I can't use my school laptop at home, which requires internet to login.

If you suspect that their iphone is hogging the bandwidth, this is what you do.

Play a video while their iPHones are connected to the network.

Or do a speed check -> http://www.speedtest.net/...dtest.net/

Then do the same test with their iPhones not connected to the network.

To be honest, i doubt it is their iPhones. But you will never know unless you test.

You can have the app to control their network speed