my plants are exteremely healthy looking but some of the leaves are curling in as well. I have plenty of tomatoes but I'm concerned that the plant is having problems

There are many possible causes. Stress can cause it. That can be a variety of reasons. Heat is a common cause. Disease also but you should see other signs if a disease. Transplant shock is another cause. In my opinion too many panic and even pull plants that will be fine. A little curling here is normal and I don't panic. Without pictures and even then it is hard to tell without seeing and observing the plant. JMO. JD

As elk said, it is usually a sign of stress of some sort and is a natural response of the plant to that stress. Once the cause of the stress is identified and corrected, if possible, it disappears. It usually does no long term damage to the plant.

The link below is to the many previous discussions on leaf curl and you will find numerous causes discussed and links to more off-site info sources.

Dave

Here is a link that might be useful: Leaf curl discussions...