I could really use some advice. I recently launched a new engagement at work and I have one other manager who is joining me. He should be handling the majority of things for his own team but things keep getting pushed onto my plate because he's MIA (we're working from home). Today, he called out and I found out there was a laundry list of items he didn't complete for his team. I'm not sure how to address these things with our supervisor without coming across as whiny or like I'm "tattling" on him, but I'm already spread thin with my own team.