I would agree with what has already been said.
How do the leaves look? Do they look strong and healthy. If so then it is likely that it is just that they have come to the end of their life, and there is likely nothing to worry about.
If the plant it's self is seeming weak then you may have a problem and the first thing to check is the roots. Even if it's healthy it may be worth taking a look at the roots.
Do you have a clear pot? If so you can get a quick visual look at the roots that show through the plastic. Do they look plump and geen (if just watered) or silvery white (if they are ready for watering again)?
If you can't see them through the pot them it would be a good idea to repot and take a look while you do. The roots should be firm and either green, white or silvery. If they are squishy then you should remove them. If they seem hollow you can also remove them, these are generally old roots.
Once you have removed any dead/squishy roots see how many are left. If there is quite a few then just pot back into a pot which is just big enough for the remaining roots.
If there are no roots left (or only a couple of very small ones) you may need to try some rescue techniques.