Subs appearing on your front page is based on how often you visit them so going to them should fix it. There are other factors in the algorithm that I dont quite know or understand , but I do know there are some esoteric and weird subs that make my front page a lot but only do because I click them often.
I noticed during and after the big protest where subs shut down that it lead to my front page becoming totally different and some subs that I forgot I even subscribed to bubbled up to the surface and this remained the same after things started coming back online again.