Fibre speed dropped to half one day after install

[#1]

Shorted lived joy.
PN delivered on their promise and installed fibre unlimited and I was getting 75 Mbps all day.
Today I am getting half that ~36 Mbps.
Only thing I did (which I consulted the install engineer about) was turn off both the openreach and PN modem overnight until about tea time.  Everything else about the setup remains the same.

[#2]

it's always better to leave them on - is there any particular reason why you wanted to switch them off?

[#3]

I was concerned about the potential fire risk, particularly with new equipment/chargers/transformers - and the fact that the openreach modem is located at the bottom of the stairs by the front door.
Speed now down to  19Mbps
Is it best to leave both on - and, out of interest, if you know, why?
More importantly how do I get the speed back up to 75, which it can clear do?

[#4]

To stop BT's system seeing a problem, it is best to leave the openreach modem powered on, but you can turn off the PN router at night then your speed won't be affected.  To get it back it normally takes an engineer visit going by a recent thread, but PN can get BT to bypass that and get them to do it remotely.  If not you will need to let DLM see a stable connection for a few days and then it will increase it again.
As for the fire risk just never have the power supply / router / modem sitting directly on the floor, especially if carpeted.  If not they will get hotter than if not raised off it and can't cool down.  So if you have them on the floor put them on something like plastic feet to help with air flow.

[#5]

the system that monitors your line could interpret restarting equipment as instability and take measures to correct it.
Now this shouldn't happen with one disconnect but it could happen.
the risk of fire should be minimal - I've never unplugged a router overnight without issue for over 10 years, last couple of years on fibre.
if you do a bt speedtest http://speedtest.btwholesale.com/ and do further diagnostics you should see your IP profile - what's that ?
and how does it compare to https://portal.plus.net/my.html?action=data_transfer_speed

[#6]

Back up to 75 Mbps
Guess it just needed time to re-establish itself.
Thanks to all for the info.  and support.

[#7]

Glad it's sorted for you

[#8]

Thanks for letting us know that's been sorted.