google fonts not coming across on mobile

Hey folks – I noticed that the Google fonts for the titles arent’ coming across on mobile for this site. Check out the heading on this page
http://queenswharf.org/queens-wharf-places/.

Notice that the page headings and the post titles is a PT Serif.

Any clues how to carry this across?

I have this in my CSS

h1, h2, h3, h4, h5, h6{
font-family: ‘PT Serif’, sans-serif;
font-weight: bold;
text-transform: none !important;
}

p{
font-family: ‘PT Sans’, sans-serif;
font-size: 18px;

}

I checked the theme settings and you don’t have Pt Sans options for <p> tags or PT Serif options for heading tags.

So I have ‘default’ for the headings and ‘helvetica neue’ for body text.

Do I need to register the google fonts I want?

How do I do this.
Cheers