website display issue

Are there any known issues relating to website text showing incorrectly on a late 2013 imac?

My website text shows fine everywhere else except on my imac - despite trying every screen resolution possible.

Yet on my imac, the text runs into images, runs over onto the next line etc...

See here https://www.ashtutors.co.uk/ in the headline and sub headline. This doesn't happen on any other machine I tried.

It looks fine on Safari but the same issue present on firefox. As the majority of the market use chrome, then I need to see what they see - and it doesn't look right.

It also looks fine on chrome and firefox on other, none Apple machines.

Any help would be appreciated.