Avenue Template: How to change the Index Thumb Titles to a custom font with CSS?

Hey! I managed to customize all the fonts on my website (link: soyolivialopez.com) but the ones on the Index Thumb Titles. I think I have tried everything, but nothing seems to change, I even managed to change the Site Title and the navigation. 

If anyone has an insight on how I can make this work, I'll be grateful forever! Thanks in advance!

You mean title under images?

.project-title {
    font-family: Tuan !important;
}