With regressive and modified progressive staining, a differentiator is used. If the differentiator is made in-house, there is the potential for it to be either too weak or too strong. Both scenarios will impact staining. If the differentiator is weaker than intended, it will remove less hematoxylin and will make the nuclei dark. Time is also important. Not enough time in a properly prepared differentiator will also leave more hematoxylin behind and will ultimately overstain the nuclei.
