Several tutorials were added for players of levels 1 to 5. They are mainly for new players, but your low level players will see them as well. Part of this change is that certain areas of the game are hidden and gradually becoming visible, as players learn more about the game. Eventually, daily quests will be added for more advanced players.
Every night about 1% of the items you have are lost, as nothing lasts forever. This applies to treats, feed, materials, tack and intermediary items. So if you have 1000 apples and you are not producing anything, you will lose around 10 apples every night, during the game reset.
The horses have realized that now that water has reached AVH, they might as well drink it. A thirsty horse will not be able to enter shows or breed, and will lose happiness each night. They require as much water as they require food (depending on their level)