Vitality's recent downfall could be attributed to Apex stepping down momentarily. He is an integral part of Vitality and even though Shox, RPK might have IGL'd a bit in the past, it isn't the same. Definitely didnt expect Complexity to lead the group though.
Apex was the brains of the Vitality team and his sudden break has left the Vitality struggling in their remaining matches in BLAST. Rpk and shox might have lead their teams but as compared to apex I don't think they have enough experience like apex does. IGL is so important, the more experienced they are the more aware they are about the opponent and their calls and you can make right calls inside the game according to that. shox was the one who lead in the match against EG so it will be interesting how he develops in the role as an igl.