ts to pleadings, to determine whether to allow the addition." 12 Wright & Miller, Fed. Prac. & Fed. P., p. 432 (3d ed. 2013)• see also Galustian v. Peter 591 F.3d 724, 729-30 (4th Cir. 2010) (collecting cases and noting that Rule 15(a) applies to amendments seeking to add parties); Frank v. U.S. West, Inc