Re: Random slow recovery
Under eating can definitely hinder recovery. In my experience, not eating enough protein will do the same even if you get the calories. I was having recovery issues and I replaced an egg in my morning scramble with about 3 oz of turkey breast and within a week the issues went away.
Another thing, too, is that you can pick up germs that your body expends energy fighting off but they never gets out of control enough to make you actually feel sick, or you'll only have mild symptoms. This can affect recovery too.