In reply to jethro kiernan:
The CA along with the softness suggests the lens is or may have become de-centred, which is when one or more of the glass elements has moved out of alignment.
Have you only just bought it?
Has the lens been knocked or dropped?
De-centring is an all too common problem, even with new lenses.
De-centring can be repaired either by Nikon or an independent repairer with an optical bench. Could be expensive though.