Conflicting CSS applied by GP

I'm working through my CSS to try and make it cleaner and noticed GP is applying H1 styling from style.css:1 and also from all.css:1.

The style.css is the H1 font configured from the customizer, but what's the all.css about?

taken from the https://mattgoddardphotography.co.uk/prints/

From style.css:1
h1 {
font-family: "Playfair Display", serif;
font-weight: 900;
text-transform: uppercase;
font-size: 26px;
margin-bottom: 25px;
}

From all.css:1 (all lines superseded by the above)
h1 {
font-size: 42px;
margin-bottom: 20px;
line-height: 1.2em;
font-weight: 400;
text-transform: none;
}

From all.css:1 again (all lines superseded by styles.css)
h1, h2, h3, h4, h5, h6 {
font-family: inherit;
font-size: 100%;
font-style: inherit;
font-weight: inherit;

I've noticed this kind of behaviour across my site for different styling elements. Where is the additional font styling coming from in GP? How can I rationalise it?

Thanks