Sour diesel, c4 clone problems

Hi, im growing 7 plants total 4 sour diesel and 3 c4 clones the clones rooted 21/2 weeks ago. i have them in a 30" x 24" closet. They r under a 26 watt cfl and a 120 watt incandescent for the moment because my grow light is on the way 18/6 "1/2 plants r in mg potting mix, and the other half r in mg organic potting soil. the temp is about 70 degrees and im using tap water from my kitchen faucet. Im noticing that the leaves r getting brown spots and brown tips. does ne 1 know why, any input is appreciated, i gladly accept any criticism.... i jus need advice please