Many leeks have solid middles.
Is this a problem?
They seem to cook OK.

The mistake was to get leek modules from a company which supplies
farmers.
They were ready to eat in July - and that is when I am normally planting
out the ones I have grown from seed.
The main value of leeks as food is to get something which can be
harvested fresh from October to April.
These are distressingly early!
--
Chris