Blueberry is well known to start off with deformed leaves. Don't fret over it, it's normal and a sign you have the "real deal". They'll grow out of it in a few weeks and will be as normal looking as the rest. I've never heard of it happening with AK47 and have grown both strains many times over the years (in fact have AK x C99 going right now!) but maybe the breeder got a bit careless with the sorting...?

I use Fox Farm products too, right down to their bags of potting soil and you can start using the Grow Big at any time but do not go crazy with the stuff. I use it with every watering but only at 2/3 +/- of what directions call for (IOW, a half to 2 thirds of a teaspoon/gal of water). You can keep the same routine for transplants but never add extra thinking they'll need it after going into a newer and bigger home, they don't and the last thing you want to do is over-fert the soil which brings on the only time one should have to flush.

Yellow spots can be caused by many probs but main ones are dropping water onto the leaves while lights are on or it may be a PH prob, usually from the tap water. If so, it's an easy fix. I use a $20 Brita water filter that drops PH from off-the-scale 9+++ down to a perfect 6.5 by only running it through the filter once. You should be able to find a cheap PH tester in any nursery or garden supply department. And lower fan leaves will naturally yellow and drop off as the plant grows so don't let a few bother you. But it is something that needs to be checked out.

Watch the watering more than anything else. Get used to the feel of a dried pot vs one that has just been watered and only water when needed, not because your clock or calender says it's time. It's good for the soil to dry out enough to wilt the plants once in a while and bad for the roots to constantly have to sit in soggy soil. Curling leaf tips are a sign of overwatering followed by shrinking rootballs and death.

Save the bloom ferts for when it's time.