Speed drop query

[#1]

Since I had fibre installed it merrily chugged away at 38Mb but all of a sudden it's dropped to about 25Mb.  Still faster than my old ADSL but a bit concerned that I've lost 13Mb of download speed when nothing on my end has changed.  Tried a reboot of the router but that didn't achieve much.  I also checked my current line speed page and it reads:
Current line speed:
26.4 Mb
Can I have my 13Mb back please 🙂

[#2]

Hi there.
Testing isn't showing any issues with your connection and the speeds are only just below your initial estimate so our suppliers will probably not investigate unless the speeds drop further.
There's a number of reasons for why the speed could have dropped but it will most likely be crosstalk which builds up in the cabinet as more users swap onto a fibre connection.