How does your film look after processing?
I use Xtol replenished, and it eventually develops floaters too. Largely I think they are made up of deposits on the storage bottle's wall, and released when the liquid is agitated from pouring in and out of it. They do, in my case, not do any harm to the process.
But that's Xtol and not D23. Sounds as though the particles appeared immediately. Is there an established D23 replenishment procedure? Do you replenish with straight developer, or is there a specific replenishing solution formulated?