Hard to tell from your pics but it appears you lost the inner crown of the plant. That area is dry and hard because its dead. You probably had crown rot but the plant survived. You may get an offshoot from below that area which will grow and flower.

It is not a disease you need to worry about. It will not spread to your other plants. You need to be careful when you water to not get water in the center of the leaves. This can cause crown rot. If you drip some water in the center crown, blot it up with a paper towel.

Jane

Oh wow, I'm so meticulous with watering...but that's possible. Okay I'll try to see if there's "any life below" and hopefully save it. If not, well, I've got 16 more to love.... Thanks so much for your info.