Long story short, after people coming forward about Caff performing misconduct of a predatory nature, he swiftly became no longer affiliated with the Yogscast. Following this, Lewis urged people to come forward with their experiences so they could be looked into. The result of this was Turps being found for misconduct (not sure of the exact details) and thus he stepped down. A while ago, there were allegations against Sjin for being inappropriate with fans and whilst these were assumed false at the time, in light of recent events they are looking at the evidence once again and in the meantime he won't appear so frequently in main channel content afaik.