Randomly Dying After Leaving the End and Losing Everything

My friend and I killed the ender dragon on a Realm. When we did and went into the portal, all our items and XP disappeared, and a message popped saying that we fell from a high place. I was able to get some of my XP back, but my friend wasn't. At one point, the end sky turned gray, similar to when a player has night vision in the end.