If you are talking about rockwool cubes, then yes the tip of the roots will die. It's caused mainly by exposure to air and light. Shouldn't harm the plant any. I grow in rockwool and see this all the time.
no hurry just seen mr green shown and his roots put my to shame dose the root ball efect the flowering stage because at harvest im only get about half once per plant @3 feet tall 3 part general hydro and awsome blossom ro water any advice