Nice and healthy looking you say? I would ditch the spike and start to look at some feeding if your soil isn't pre mixed with plant food. Also Clang 80 has a good point that I missed....lights. # weeks is a good time to give them low doses of nutes...low and then work your way up. If you have a ton of roots then things sound good, and sometimes a transplant will start a spurt. I've grown Blue Berry it can be tough and a slow starter but it's a great plant once it gets going....good luck.