Which version of the firmware are you using? Most Smart Hubs tend to ship with an old version and are then updated - though even the latest public version needs some work to it (including to the modem code) and there is a newer firmware version being tested.
Had it been a long time sinc your HG612 had last resynced? The hotter weather now can also cause the line attenuation to increase which also leads to slower speeds. If so, when you put the HG612 back on the line you are also likely to get lower speeds than before
The HH6 firmware was dated 12/5/16 - it did update itself from a previous version it was shipped with that had an April date.
Don't know the firmware number - being impatient I have now swapped out the HH6 again.
With the HG612/HH4 set up I historically have had an IP Profile of around 65/20 (I'll use round numbers for simplicity) for almost 3 years. The actual speed reported by the OR speed checker is normally around 63/14. There has been very little deviation. I have been lucky and had a very stable connection since OR fixed a major (and I mean major) problem with their ducts/wiring in our road over 3 years ago. Prior to that the connection was flaky (putting it kindly).
Before the very latest swap the OR speed checker reported the HH6 as having an IP profile of 59/20 with actual speed of 53/12. I then swapped the HG612/HH4 combination in again and the IP profile immediately improved to 62/20 and the actual speed to 59/13. The HH6 itself reports sync of 61/14 and maximum attainable rates of 60/14. I also checked the speed using another website and this validated the speeds indicated by the OR checker
It seems to me that my original surmise that the HH6 is junk may be correct.
I have managed to lose some of my previous connection speed and have also paid BT for the privilege.
