Graphene 1.8 help

I have just updated to the latest version of this theme and prior to the update all my <h> tags were bolder than the normal text. With the update all my <h> tags are no longer bold. I have tried adding custom css to try to make the tags bold but it does not work. Does anyone using the theme have any ideas?

An example is https://computerlearnhow.com/hard-drive-failure-repair-and-recover-data if you look at the first h2 tag this should be bolder.

Many thanks