BT Hub upgrade cause the upload speed to drop back

During the BT Hub upgrade process, the upload speed showed a great improvement from 5.8Mbs to 6.5 Mbs. But the upload speed dropped back when the upgrade process ended. Why is it so? Please help.

During the BT Hub upgrade process, the upload speed showed a great improvement from 5.8Mbs to 6.5 Mbs. But the upload speed dropped back when the upgrade process ended. Why is it so? Please help.
The drop in the upgrade speed may be as a result of several reasons, some which are as follows:
-Experttechyv
You really don’t have control over your internet’s actual speed. The speed is affected by many different factors happening to the network in real-time. One of the many factors affecting your connection’s speed is the current load of the network. If you are uploading your content during night time, since most people are at home during these times, the possibility of a slow network is there.
For me, the best time to upload or download content is at dawn because only less people are online during these times. I’ve tested it a lot. My monthly plan speed is only 3 Mbps but when I download something at dawn, I usually get something around 4 to 6 Mbps and it is really awesome.
Another factor that can affect your speed is the weather and this is really true when you are using a wireless broadband internet like LTE. If you are using DSL or fiber, weather is not a factor. Speed is constant and stable with these two. Another factor that can affect your speed is if the network is undergoing maintenance or upgrading their system.
Be ready because it will really test your patience.