I grew Shasta Daisies up until 20 years ago and I think the center on mine died out too. Dividing it will help. Looks like you can split that clump into around 7 plants. This species is actually native to Alaska, so growing it in hot, humid North Carolina summers might be stressing it? It says it will grow in cold regions duh, it's native to Alaska, so I would hope so. How much growth has your clump put on annually? It really doesn't look that bad. You could prop up the stems to hide the brown spot if you give any garden tours Lol.

I think there might still be time to do a 'Chelsea Chop'...take off a third of the height - you don't need to cut every stem, do a layered look. Then lift the whole clump and divide next spring. Like asters, I think these really benefit from dividing every 3 years or so.

caveat - sez me, who doesn't grow them, although I did sow seed last year, of the exact same variety - 'Alaska'.

I have been very much enjoying this series of videos

https://www.youtube.com/@perennial-garden

" This species is actually native to Alaska "

Sorry, that is not correct. This plant is not native to anywhere, let alone Alaska :-) 'Alaska' is a cultivar of Leucanthemum superbum, a hybrid daisy created by Luther Burbank in California in 1890. Original parent species are European wildflowers.

The cultivar name, along with the common name of Shasta daisy, is a reference to the snowy white color of the flowers.

While extremely easy to grow (and start from seed), the plants are not particularly long lived, with the clumps thinning or dying off after a couple of years. And because they tend to get tall, lanky and kind of floppy, I have always thought they benefit from a mid spring Chelsea Chop myself!