ConcernedApe, the developer of Stardew Valley, has put out a performance patch for the Switch version of the game.

The patch fixes the frame rate issue that occurs with bigger farms, so if you were having horrible frame rate this patch should do the trick.

Stardew Valley Nintendo Switch users: the performance patch is now live, this should fix the frame rate issue with bigger farms

— ConcernedApe (@ConcernedApe) January 21, 2019