Am I over watering and a few other questions

Hello fellow medical growers, I am growing " First two photos Medical Seeds Sour Diesel," " Second two photos Nirvana's Jock Horror," "Third photo Nirvana's Short Rider" All 12 days in from sprout. Ok so I am growin the SD and JH in GH Waterfarms I on a watering schedule of 2 hours 2 hours off in a 24 hour period I am on a 18/6 light schedule right now. They seem to be on schedule with there growth rates. I change out the reservoirs every two weeks with fresh nutrients following the GH Flora Series Recirculating schedule as I always have in the past. I've had very successful grows using this same regimen. First time successfully germinating the "Medical seeds SD" It seems that these genetics are not the best. But I figured I ask since it seems I have always had this problem with the leaf tips curling under and the tips turning brown and crispy. I want my beauties to be nice and green and flourishing with healthyness but like i've said in the past that they've always made it past this point just fine but it seems in there "adult" times they've always started turning really nice and green But the leaves at the bottom always yellowing and dying. This is my thrid time growing the jock horror its in my journals. First time SD and fourth time short rider I believe. And I've grown 2 successful Black Jack plants from nirvana. i've only had one successful Shortrider and that was in hydro. Every successful grow i've done has been in the GH Waterfarms. Never had a plant die besides th two other SD's I tried before and they didnt get past seedling. But i've never had a successful grow in soil. I just cant grow stuff in soil (look at my poor shortrider) what am I doing wrong? I water when first few inches of soil get dry but im using a mix of worm castings and vermiculite and organic potting soil. No nutes on this "lady" yet. But is the mixture too thick. And how about my other two ladys and there brown curling crispy tips in my hydo? Can anybody help me with a solution to these problems? I hope this all makes sense.

EDIT: The pictures posted in wrong order. First and last is SD, Second is SR and the thrid and second to the last is JH

They look to me like they are getting a little "light burn" ?? Just a thought, check the distance to your light. Unless Nutes are getting to be a little hot for the lil buggers.