Prior to the line going down my typical download speed was 35 Gb/s now I am only getting 18 Gb/s. I have rebooted both the modem and the hub with no effect. Any ideas?
18Gb/s is still faster than all the connections in my town combined. You should be happy with that.
If you mean 18mbps, then you will just have to wait for DLM to do its thing and increase your profile, as it would have lowered it to maintain stabililty. This can take a few days to a few weeks.
While waiting for DLM to do its thing (as Deathtrap mentions):
Don't touch the modem. (white Openreach box)
Disconnect and reconnect the router )black BT HomeHub) each morning (from the web interface), or power off/on if that is easier.
Playing with the modem can be seen by DLM as problems on the line, so it might keep your speed low.
Sometimes DLM allows your low level sync speed to increase (usually overnight), but that increase is not noticed at the higher level and your IP profile remains low (matching your old sync speed) ... so called 'stale IP profile'. Disconnecting/reconnecting the router will force the IP profile to match any improved sync speed.