Diagnosing plant problems is a real challenge, especially without any pictures and more importantly without being able to be on site. There could be many below ground physical variables that may be at play unless you know as a fact that there aren't. With this thought in mind, you have to take into consideration how deep the roots will potentially travel into the soil so knowing what's below is pretty much an unknown unless you're willing to dig, dig, dig until you can find where the deepest root terminates.
Just suppose that you DO know what's below in the soil and determine that there's no problems there. Now you have to look for other similarities/differences and keep ruling things out. I don't know about the cold tolerance that each of those varieties posess, but I would bet that they all had to try to survive an exceptionally cold winter. Maybe the Nugget is less cold hardy than the others? Lots of detective work involved here so sorry, that's all I got.