I think it's safe to assume that most or all MSCs have editors who work on holidays. A lot of them seem to get paid by amount of work completed rather than by the hour, and at least some can set their own hours as per contract, so I am not sure if holiday pay really even applies. If you know for a fact that these editors work in the office, that's one thing, but many editors work from home. Either way, I wouldn't be hugely concerned about it.
Though it's not an excuse to slack off, the MSCs try to give themselves a window for situations like this, and it's usually a day or more. Depending on the MSC, though, you might experience a payment deduction for the report being late. It depends on how forgiving they decide to be. Good luck, and I hope you get over those blues soon!