Trouble with new gigabit fiber setup

I recently switched to Telus to get gigabit fiber. It was amazing when I set it up, for all of 5 minutes. Was getting >300mbps in every room. 500-600mbps next to the modem, which is the Telus wifi hub modem. The second I added a second device (first was samsung s22), it dropped to <200mbps EVERYWHERE in the house. I figured i'd give it the weekend. This evening, my wife was watching some netflix on her tablet, I couldn't even connect to the 5G on my desktop or S22. Everything is Wifi, we have 8 devices total, but only ever have 3-4 connected at once (2 phones, 2 computers). We tried the router/modem from our old provider as well. It is only better in that it actually separates the 5GHz and 2.4GHz channels. I tested this as I type this post, 54mbps download.... On gigabit fiber. What can I do??