I'd check the roots to see how congested they are, first - if they are, potting them in to bigger pots/cells will stop them getting sick and dying. 6-8 weeks is a long time to keep their roots from spreading out. Its like childrens shoes, little feet need space to grow, the same applies with roots
By the time it comes to put them in, they'll have doubled in size and looked like they've been in for ages.
I've just done the same with my hanging basket plants, btw.