On my laptop, which supports both frequencies, the speeds for both used to be similar and reaching the max speed of my broadband connection (36Mbps). On my phone, which only supports 2.4Ghz, I don't remember ever being able to get more than 8Mbps - I've tried to research whether it's some limitation of the phone's wifi (it's a cheaper Motorola pone), but I've given up and lived with it.
Now, I just noticed a drastic drop in the speed of 2.4Ghz on both my laptop and phone. At the moment, the laptop is showing about 1.33Mbps speed and phone 0.56Mbps. I experimented with manual channel selection for 2.4Ghz but no luck (by the way - the automatic "smart wireless" didn't actually choose the least crowded channel).
There are only 2 changes that happened recently. I had an update pushed to my hub as I was having issues with the 5Ghz band. I also added a wired connection to my desktop, but at the moment as I'm doing these tests this is inactive.
What could be the cause of these strange happenings?