Episode 14 has been pushed back this week because the network and the production company have agreed that with all the post-production work the show requires, it would be better to give themselves additional time instead of ending their show haphazardly. This means that next week, you’ll have three episodes: 14 on Friday and 15 and 16 on Saturday.
(Provided they don’t have to delay those, too.)
P.S. Gong Yoo is just exhausted, not sick. Best of luck to him and the rest of the cast and crew as they try to wrap up the show.