Why does my download speed tank after a few minutes of downloading?

Been getting into downloading games for my 360 and I’m using Mainly ROMSFUN for my games which is mostly working but specific games which seem random start off with a good download speed 10mb/s and then after a minute or two the speed just tanks down to 5 or 4kb/s which is an insane drop.

I’ve tried multiple sites to see and all those games that tank also tank on there but then I go to download smth else and it’s back to a normal download speed, is this to do with some kind of seeding or is my internet wack?