Sounds like it could be a case of under humidification. A few questions though:
1. I am guessing you mean hard in relation to what you remember when you 1st got them?
2. When you smoke one, does it burn 'hot' (faster) than you are used too?
3. Also, when you smoke them, do you get any bitter spots in the smoke? This is also a sign of a dry cigar.
Sometimes over humidification can also cause hard cigars (absorb water and expand). If you have a way to get a hygrometer, this would help tell exactly what is the case. However, seeing as it is the cold dry season of winter, I doubt this is the case. I would advise to make sure your humidification unit is charged more often than usual with distilled water. Also, try to keep opening the humidor down to a minimum to keep the inside humidity stable (I know this can sometimes be hard to do :dr ).
All in all, if the cigars are still smoking well, than you don't have too much to worry about. Just keep the humidification unit charged and enjoy them smokes :ss