When you change something and you get something new going on with your body, it's probably the change. Boot camps tend to be pretty strenuous workouts. You don't say what your fitness level or amount of vigorous activity was before, so it's hard to say if this is just too much too soon for you, but it is different than your normal routine and you've probably stressed your muscles and they're telling you so. As for hydration, if you severely increase exercise, while hydration is essential, so are electrolytes, especially potassium and magnesium, which help relax the muscles. I'd also ask if you're warming up first or doing any stretching, and if you're cooling down and doing any stretching. As for protein, that can help with recovery from resistance exercise but a protein supplement isn't a necessity, it's a shortcut for people without the time to eat several meals a day if they engage in vigorous muscle work.