Day 7 from seed, planted in a .3 gal air pot in a Rapid Rooter plug. Using nothing but PH'd water and letting the FoxFarm Ocean Forest do its thing. I've yet to try Grandaddy Purple, which is super exciting. I can't wait to see how beautiful this one turns out!
3 best things for strong stems. Proper strong lighting, Specifically high-end leds I've noticed help a lot. Fans gently moving the plants to stress the stems a little and bulk them up. Lastly a silica supplement. Silica helps boost your plants resistance to many different things and this includes helping strengthen the stems.