I've seen people bring candy into the exam room in their clear bags. I don't especially advocate for this option, but eating some candy in the break could give an adequate sugar rush (before the crash) in those final two sections.
Don't be concerned with one drop especially if you noticed the lack of focus. 4 tests is also too small of a sample size to be positive of where you are at exactly. Keep on blind reviewing and check back in a few tests. Totally normal to see some drops.