Hello ! I would not let them in the same DWC as the roots are going to fight for the space so you will have a smaller plant or 2. The roots are not the only one that will probably suffer from the space as you have 3 seedling in the same space so that mean you will have to manage 3 cannopy on the same little area ( you should think about LST or Scrog in your case). You can also wait for the seedling to be little threes before trying to move them in individual pots. I hope it will help you 😁👍