I'm growing camillia sinensis (tea) hydroponicaly and, I have a small sprout growing, which is only about 2 to 3 weeks old. The stem has a purple/brown sort of color to it near the bottom, and is green near the top. Is this normal, like it is with other plants? Am I giving it too much of something?

this is what im giving it:

18hrs of flourescant light per day, its in a drip systen that turns on every 2 hours for 15 minutes, im using flora nutrients (really lightly as to not hurt the young plants).

So are the purplue/brown stems something I should worry about?

Thanks!

Very often one camellia species has different variation on stem, leaves, flower color and growth habit.