This one has been a bit of a puzzler but the server provider has been looking at this since it was flagged up as a possible issue.
Avast report if an email address is linked to any released data lists current or historic (using them will subscribe you to them) but entering email to https://haveibeenpwned.com/ will give you similar data.
Wrexham.com does appear on a ‘new’ list of 25,000 sites however the figures involved didn’t seem to match. There are some email addresses we have checked that flag up, but others (my own for this account for example) do not. There are a few other sites that will trigger alerts from sites that have never been used (again as a personal example I am listed on an issue about online game Evony that I have never heard of) , so it is unclear what the reality of any issue is – and it is stated as ‘unverified’ on the above link with commentary from some experts such data is over egged.
After spending some time investigating it appears the data referenced could have came from the very old vBulletin software the forums ran on, and were moved from back in 2014-15. One of the reasons for moving was for security. On moving from vBulletin to this current software all users had to set new passwords, and to be clear that process would mean any passwords would be new – and even if old ones reused the ‘hash’ or mathematical stored version would be ‘salted’ so would not appear as the same.
There is no proof that was the case but would be a best guess.
Out of an abundance of caution we would suggest (here and anywhere!) if you are still using passwords from 2012-2015 then they should be changed, and as always would suggest using strong passwords.