Product Page Title - Uneditable in Site Styles

Site URL: https://www.nourish.melbourne

Could anyone please let me know how I can change the size of the Header Title on my Products page?

At the moment it reads much too small compared with the rest of my site. I cannot seem to edit the title in Site Styles either.

Please see screenshot for example - thanks in advance for your help

Version 7.1

www.nourish.melbourne