Recent updates have caused the custom font and styling to not be applied to to the search widget button text.

To fix this, find this section of CSS:

.widget_search input#searchsubmit {
    font-family: 'Dancing Script';
    height: 45px !important;
    border: 0;
    color: #52576d;
    background: #f4d1d8;
    font-size: 25px;
    border-radius: 0;
    padding-left: 5px;
    padding-top: 7px;
}

And replace it with this:

.widget_search input#searchsubmit {
    font-family: 'Dancing Script' !important; /*Updated 20/02/18*/
    height: 45px !important;
    border: 0;
    color: #52576d;
    background: #f4d1d8;
    font-size: 20px; /*Updated 20/02/18*/
    letter-spacing: 0 !important; /*Added 20/02/18*/
    border-radius: 0;
    padding-left: 5px;
    padding-top: 7px;
}