So I bought some nutrients, will these work?

So there wasnt much word on Scott's Manure and Humus product.

Its a 15/15/15 mix. Will this be ok to use or will it be too nutrient heavy?

I bought Promix seedling starter for my seedlings. I heard this stuff works pretty well.

I'm still confused as to what nutrients to use at what stages. I'll be using the promix for the germinated seedlings, but at what point do I switch over to the manure/humus? And what do I mix the manure/humus with?

Ok so I'm going to return the 15/15/15 because I've read its too hot with nutrients.

I'm going to try and get a 10/10/10 manure and humus w/ perilite.

Also, I answered all of those questions. The only thing I'm confused about now is when do I perform the flushes?