"[T]he most common allegations raised against 401(k) plan fiduciaries [include]: [1] Failure to leverage plan profile to reduce fees. [2] Selecting excessive expense fund share classes. [3] Using plan assets to pay excessive recordkeeper compensation. [4] Offering money market funds rather than higher-yield stable value funds. [5] Failing to monitor fund performance and removing imprudent funds at least annually. [6] Failing to engage in a formal request for proposal with plan vendors at least triennially."