Since the season started I have been doing almost every Vex Strike Force that happened, and not a single one has dropped one of the Season 21 exotics. I have all exotics unlocked except for those. Most of my friend group and others had also voiced that they have done multiple Vex Strikes with no new exotic drops, only duplicates. Is this a bug or did bungie decide to not add them to that loot pool just yet?