Changing smiley size

I’ve been using a custom smiley plugin with no problems. However, lately, the smileys have been showing far, too small across the site. The plugin hasn’t been updated so I don't think it's a plugin issue, and I’ve searched for and tried several CSS suggestions, but nothing works. Any help would be appreciated.

Thanks in advance.
https://www.simfansuk.com/wp/sagebrush-rise/