iPhone causes latency issues when streaming on my Samsung TV

If I am watching a 2k or 4K movie stream with a Firestick on my Samsung TV, it immediately goes into a stutter/lag if my wife opens up YouTube, Facebook or Messenger on her iPhone 13 Pro. Once she shuts it down, everything streams fine. (I can't guarantee this, but I swear it will also hog the BW / latency on her iPad as well.) If either, or both devices are idle. I don't see the lag. Tried several players, playlists, VPN on & off, and VLC external video player. Recently updated to Xfi 1.2G. Worst case BW that I see was in the 50 MB's, but pings are in the 60 to 70 range. (ExpressVPN). This is with an Apple device causing the lag on the TV. Best case w/o VPN may get to 200 Mbps, but pings are still above 50, and without an apple device signed in. Is this due to Tizon, Firestick 4k or Apple OS? thoughts?