I can only change the font size for post title on desktop, not mobile. The mobile version of my post title seems to appear smaller than the font for body text. How can I make the font size bigger for post title in mobile version?

Basically it happens to all my posts on my site, but here's just one post just as an example. Make sure you view it on mobile: https://lowcarbcrave.com/keto-caramel-sauce/

I've attached two screenshots. One is from my website lowcarbcrave.com that is using the Soledad theme and the other is another one of my websites using a different theme. As you can see, the post title is much smaller than it should be and needs to be bigger so that it readable to users. Is it possible to make the font bigger? On desktop version the font size is completely fine, it's just the mobile version that I want to change.