Jimmy, below I linked to a Google Search about why tomato cores appear. Sometimes it's a trait of a particular variety, but most of the time it's due to weather and stresses as you'll see when you read those first links in the Google search.

Hybrid or OP it makes no difference as to the factors that can induce hard cores, so I'm not sure why only your CP is showing them.

I've grown Cherokee Purple many times and was one of the first to receive seeds since they were sent to me by Craig LeHoullier in Raleigh and he received the seeds from John Green in TN and it was Craig, whom I've know for about 23 years now, who named it.

I hope the Google links will give you a better idea of what can cause cores to form, but I will say that I've never seen cores with CP nor Indian Stripe, a version of CP, since about 1992 for CP and maybe about 2003 for IS.

Carolyn

Here is a link that might be useful: Google Search; hard tomato cores