Last week (Wednesday) when the guild buffs disappeared after the release I did not start them again for 24 hours because I wanted to make sure they were really fixed. So, I started them again at about 11:30 am PST on Thursday. They should have been still in until tomorrow at that time… however this morning when I log in, our buffs are gone.
Just to check, was this done on Thursday 11th April last week? Also, did you check how much time was left prior to this?