I've actually had this issue for a while but it never really bothered me. Anyway, When the player gets a certain blocks way from blocks, a white outline will appear. I'm not really sure why this happened. It kinda just happened after opening the game for the first time in a while. I don't have any texture packs, resource packs installed other than the ones that come with the game. I think the issue started around 1.14 and consistently did not change through the updates.