When i worm my wee peas they are ages from a week old and older and all has went just fine, sosix weeks old is ok
Have you wormed them at all yet? try some scrambled eggs and if he eats that i bet he is just holding out on you waiting for thew meal worms but being fuzzed up could be a sign of illness coming on lick cocci and mabe worms but don't you have them penned in a brooder? if so i do not think they would have worms as there would be no way for them to get them from the ground like mine can
My pea is in a cage on the ground and he loves mealy worms. He will grab them out of my fingers !