What happened is probably the media is fairly homogenous in terms of nutrients/vitamins, and it's just the charcoal that settled out as it cooled. Happens to me sometimes. But the charcoal is very nice to have evenly mixed as it will come in handy to neutralize some exudates to save you from needing to replate unnecessarily.
A good practice is to gently swirl media as it cools, to keep things distributed. Best practice is to make sure things are fully dissolved at the start
But charcoal will usually always settle as it can never really dissolve.
But for now, if your vessels allow, you should be able to reheat the media to melt it (obviously make sure to keep them sterile), and then just make sure you swirl before it sets again.