Hi Dave,
It's normally the reverse that we hear about---a bit getting lighter and not darker. Don't condition it if it does need it. There are many factors such as lifestyle, body chemistry, frequently of washing, hardness of water, etc. that affect the life of a system. Eventually every piece needs conditioning but don't do it until your unit absolutely needs it. Then use a conditioner such as Blue Max or a similar product. It may be that your regular normal hair has gotten lighter due to the normal oxidation process. This is making your hair piece look darker that it was 2 months ago. I suggest using a hair color blender. I 'blends' the color of your hair to the color of the hair piece. You just put it on a comb and comb the hair where the hair of the unit meets your own hair. Good products to use are 'Just For Men' and 'Back 2 Natural'
Regards,
John