What are reasons for just slightly high protein in the blood in the CBC (mine was 8.6) high normal is 8.4. Just curious - all other labs normal?

Labs as read by lab. This is why you have a doctor. To interpret labs and to know when something has meaning or not. In a lab report where every thing is normal then this incidental finding is meaningless. You may have been fasting and slightly dehydrated thus this important test show minimal normal slightly high. It is not a condition, disease or anything to worry about.
? Might even be actually normal. The lab values are not absolutely precise. If concerned ask your dr. If the clinical picture is normal this may be of no significance.