biobizz soil questions

Hi about to run some devine storm and platinum gushers from in house genetics and I have bought a bag of biobizz light mix for initial seedling stage and all mix to transplant into, my question is how long should I wait to transplant the plants from lightmix into all mix? because I hear the all mix can be a bit hot for some seedlings initially so want to play it safe, I plan on starting in 2litre pots and then transplanting into a 15litre fabric pot to finish in. Should I just do the 2litre pot in light mix and go into the 15litre with all mix and maybe add some perlite?
thanks in advance!

Can I ask did you ever find out an answer or how did it work for you? Im starting soon and that was my exact question!