Everyone basically said the same thing, but they're all correct. If I may be a little more precise, it's a vital necessity to consider others well-being and speak directly to all involved, to express what's bothering you and that you need personal time to sort things out. You can always write another day, life and personal health is more important at the end of the day.

If your writer's block and burnout isn't backed up by anything bigger, perhaps it is still a sign that you need to do something else. (Exercise, sleep, eat more etc.) And if you think that will effect your output and make things move slower, same rule above applies, just say so. I can assure you, speaking is the best thing you can do. As no one worthwhile gets upset when your honest and personable. 

Don't message a sidebar that no one will read. Don't go radio silent. Don't shift blame and make it about someone else. Whether it's a specific RP that you lost interest in, or have burnout from writing in general. Be direct, be honest and say what you personally need to do. And don't be afraid to give details if you have them. (I.E, How long of a break you may need.)