Hi James,
If that is a base Nucleus you might have only 4 GB of RAM. One quick and easy upgrade is to increase the memory to 8 GB and see if the situation improves.
As mentioned in another thread:
As to what RAM to use, again I will post a link to a discuss that gives a suggestion from one of the Devs. The RAM is still available.
You should replace the old RAM with the new, I would not try and run both memory modules as that could introduce issues.