Biobizz all mix too strong?

I've chosen to grow in Biobizz all mix, but I think it'll be too strong for my cuts as they have only rooted the small rockwool cubes, so basicly hardly any roots and don't need feeding, so would it be best to put them into b&Q verve sowing and cutting compost in small pots, until they've rooted the small pots, then transplant into bigger pots with biobizz all mix in? my mate put his cuttings straight into biobizz all mix and it burnt and killed them all. I don't want that lol. Next he's going to try to use biobizz light mix for first 2 weeks then repot into big pots full of biobizz all mix. I don't know what to do. I personally think my idea is better than my mates because they is no chance ill burn them lol. What do you guys think?

I used to grow in canna coco, but now decided to try using mud as I heard it's less messing about.

thanks