This is my first grow... my one plant is a little more than 3 weeks old from germ... got it from bagseed. This plant is sort of a practice grow before I invest in some decent seeds. The other day i noticed brown spots on the very bottom leaves, also 2 leaves have yellowing tips. The top leaves look fine... although I could be wrong I'm pretty noob. I'm growing it in a DWC bubbleponics system under 2 42w CFLS. I'm giving it 1/3 str nutes. PH is around 5.7ish. Also, how often should i flush my system out? Hope its not deathly ill or anything 
