I got the 3 pack from Costco but still have dead spots in my house. Seems the wireless backhaul is not getting a strong connection to the other nodes and hardwiring isn't an option. What add on units

Just bought the AXE5300 3 pack Deco mesh from Costco. Initial speeds are increased compared to my Orbi but I'm getting a weak signal regarding wireless backhaul (only 2 bars in "Brian's Office"). I'm