How can I tell which device is using the most data?

I've seen a lot of posts from people saying their data usage spiked randomly with no change in how/when they watch TV, stream, download, etc. Is there a way to find out which device is allegedly making the data usage so high? We've always stayed in the 400-600GB monthly range. This month we're at 1100GB with 8 days left in the billing cycle. We haven't added any devices, don't have any suspicious connections, etc. I have downloaded a few games, but that's not out of the ordinary. Just wondering if the data spike is legit or if we're getting ripped off.