check your lights. if all is OK there, check your genetics.
LOL, if it were only that simple.
I've found that genetics are probably the biggest factor, but lighting is not the #2. In my experience container size (and how efficiently you use it - IE: gradual "step-up" transplants to grow the root ball a little at a time) is the second most important factor in soil, probably more accurately called root development.
Also, in my current run I've discovered that HPS lights don't produce as tight nugs as 3K halides, which in my case are producing considerably stouter buds in Northern Skunk clones.
Still, at the end of the day, genetics are the biggest factor.
On another note this is my second run with SS AK-47 looking for a keeper, and I must say that most of the AK is a little leafier than what I expected, even though this round I deliberately ran it in a mix with low nutritive content and mucho perlite, still HUGE buds, no doubt about that. I'm on day 50 and the AK in my SCROG has buds almost the size of a mason jar.
PS: I'd love to see some pics of your white russian!