I think you need to be thankful for the fine flow and put another super on! Nectar takes way more room to store than cured honey. Sounds like those bottom two boxes are all in use. At least two supers are appropriate and they can't fill em if they aren't on the stack! If you are drawing foundation, consider putting a box on underneath the super being drawn to get them working in both. I just have a little pollen coming in! My honey flow is at least a couple weeks off.