In this paper, we propose a secondary consensus-based control layer for current sharing and voltage balancing in DC microGrids (mGs). Differently from existing approaches based on droop control, we assume decentralized Plug-and-Play (PnP) controllers at the primary level as they provide voltage stabilization and their design complexity is independent of the mG size. We analyze the behavior of the closed-loop mG by approximating local primary control loops with either unitary gains or first-order transfer functions. Besides proving stability, current sharing and voltage balancing in the asymptotic régime, we describe how to design secondary controllers in a PnP fashion when distributed generation units are added or removed. Theoretical results are complemented by simulations using a 5-DGUs mG implemented in Simulink/PLECS.