I have set up a hydro system to grow lettuce outdoors on my patio here in Florida. My lettuce has been growing very stalky and not forming into nice tight heads. It flops over the sides of my PVC pipes. I have followed suggestions on youtube by MHP gardner which was very helpful but his lettuce grew into well formed heads with a deeper green color. I started with black seeded simpson lettuce but have also added butter crunch in hopes of having better luck getting heads to form but so far they have a lot of stem too. Any ideas on this problem?