transplant/nute questions

I have had 5 bagseed plants under a 400W HPS for a month now and they are 5-7inches tall.

I am planning on transplanting them to bigger pots(16oz cups now) and starting them on a 12/12 flowering cycle.

How long before I add nutes after transplanting into a bigger pot?(Scotts soil)

What nutes should I get? Flowering specific nutes?

I've read to start with a 1/4 recommended on the bottle and work your way up, do I do this every watering?

Flowering nutes should have a strong phosphorus level to them (the middle number) I use extremely high p content myself, even though I've been told not to... but it actually seems okay so long as I don't use it at full strength.
What are you transplanting them into exactly also?
just basic potting soil?
or something else?
might might kind of change the answer I'd give a little to the other questions...
other than to say the 1/4 dose to start seems safer it prevents you from nute burning right off
and you can slowly raise it and see what the plant likes the best.

I plan on putting them into a 1gallon pot with Scotts potting soil, the same soil I used to plant in the cups.(unless this is bad?)

I'm assuming the only place to get the proper nutrients would be at my local hydroponics store? I'm really clueless about all this but according to the "how to grow mj" guide it says to use a 5-15-15 for the flowering stage, but his plants were much bigger and older than mine, so I am not sure if this is what would be good for me.

I would transplant about 1 week before you start your 12/12 cycle. Be very gentle and your plant will notice little more that more room to grow

Continue veg nutes the first week of flowering then your good to start your flowering/bloom nutes. I like to start at 50% recommended dosage.