I've emailed you as a dissatisfied TPG/NBN customer. I'm paying $69.99 a month to TPG for your NBN 50 plan which promised average nightly speeds of 48Mbps but lately it has been abysmal.
Welcome to the community!
Thanks for raising this to us, we're sad to know that you're having issues with the speed of the service. Based on the given details I assumed that all the devices affected with the issue are connected via Wi-Fi. Devices connected by Wi-Fi may experience slower speeds than those connected by Ethernet cable, for testing purposes and to identify the actual speed of the service please run a speed test using the laptop connected via LAN/Ethernet cable and post the screenshot on this thread.
On the other hand, we did an article that you may find helpful, this will guide you on how to improve the wireless connection at home. Please see links below.
Let us know how it will go.