It happens all the time. Pinch out or cut off the smaller plants and use them in salads. You don't have to do it all at once. Start by removing the smallest plants to make them a couple of inches apart ... keep thinning as they grow until they are the recommended 4-6 inches apart.

They certainly look ready to be pricked out into individual pots. Lift up a clump and gently pull the individual plants apart and replant each in its own pot. Or discard some if you don't need that many. Without knowing where you live it is hard to know what to tell you to do next. In a mild climate they could go outdoors or into an unheated glasshouse after they have settled into their pots. Catnip is pretty hardy. But if you have cold winters they probably need to stay inside in a cool place with plenty of light.

I no longer grow corn due to the tree rats! The raccoons are just as bad. But I refuse to give up on my tomatoes. IIRC the three sisters worked off vining squashes and the hills were more on the order of a yard apart. As close as these are planted thin the hills to 1 plant per hill, a scissors at the ground level like suggested above and yesterday is better than today and tomorrow is better late than never. Part of the process was also staggered planting with all the plants directly seeded; so the corn got enough jump to grow out above the squashes and be tall enough for the beans to have something to climb without overtopping an potentially smoothering the corn stalks. There was a balance to it all and a matter of careful timing. Interesting corn fact: it is estimated that the Aztec empire whose staple was maize prospered on yields of something like 15 or 16 bushels per acre. Most commercial farmers now get around 200.

They seem lots thicker ==>>> they are annuals ... so they arent older.. thicker only means you had more seed heads.. and you did strew them around ... so i guess i dont know why it surprises you ... i planted the plain old.. plain old.. about 10 years ago .. they are still around.. they get nothing from me.. except for benign neglect ... lol ... so i doubt you need to do anything ... i surely wouldnt be out there trying to separate clumps of multiples .... unless you just want to be out there.. and experiment ... which is always a good way to learn ... if i wanted to spread them even further.. i might take whole clumps .. and move them around .. i used to do that with all kinds of plants.. especially on rainy days ... so they would water themselves in.. i too used to have spring fever in a bad way ... lol .. ken