Seedlings into hydro, yellowing

Hi all,
First post but been lurking for a bit now. This is my first hydro grow and I'm having an issue. I just moved some seedlings (started in rockwool cubes) into my ebb & grow system. They germ'd on 3/1 and by 3/13 had 2-3" of root coming out of the rockwool. They went into the buckets on 3/15. The rockwool just barely touches the water during a flood. The top stays pretty dry. I have my control elevated about 1" and plan to drop it down after a couple more days. That will keep the water well below the RW.
I'm using FoxFarm GB and BB (hydro version of GB) and started out with the recommended EC/PPM of 1.0/700. I started to see a little yellowing within a couple days and did some more research. I can't find a cut and dry answer but general concensus seems to be 700ppm is way too high. For now, I dropped the nutes to 400ppm.

Grow Info:
pH - 5.9-6.0
Room Temp - 77-83f
RH - 55%
Res Temp - 67f
Light - 1000w about 5 feet from plants for now
Water - RO/DI
CO2 - 1500ppm (free, thanks to my kerosene heater. It's not in the room though )
Flood Cycle - 4 times/day for 15 mins (I had originally started at 8 times/day on advice from a friend, think that was too many)

Tons of ventialtion and all in all they are growing well. I'll try to get a pic up ASAP. Anyone with experience using FoxFarm want to chime in? I'm debating dumping the res and going with plain water for a week to flush things out, but being new to hydro I don't want to do anything until I identify the prob. Pics will be up in a moment...

Thanks!

You got pics? Its hard to say.

Hmm...pic ended up in it's own thread. Not sure how I managed that.


First up is GH White Widow. Hard to see but the yellowing is on the outside edge of the leaves AND along the "spine" of each leaf.

Next up is GH Cheese. Looks way worse in person and is yellowing rapidly!

Dam this is killing me! Since this morning they look considerably worse. Spent some more time looking around and can't seem to figure it out. Some people say if the tips aren't burnt and no curling, it could actually be nutrient deficient. Then in the same post "experienced" growers say it's over fed. Gahhh!!!! Still thinking of running plain water...I just don't know. Also thinking of buying some more friggin soil and forgetting this hydro stuff...lol.

Its hard to figure out sometimes. I've found over feeding can cause a lock out of nutrients that manifest themselves as nutrient disorders. I had problems with MG deficiency when I first moved over to hydro but I think it was because of over fertilization. They should only be on light nutes at this stage though. Even 400ppm may be a bit high. You can introduce light nutrients through foliar feeding if you still think they're deficient. Another thought was maybe you could put some bubbles under the plants to keep them nice and oxygenated while they flood or better yet use bubbles and keep them flooded.

Thanks Rusty. It's a tough call. I think I'll flush tonight and tomorrow and see if that helps. If it's a deficiency, it should show even more. If it's over nute'd, it should get better. I figure the plants can tolerate under better than over so I'll try that first.

Bubbles is something I've thought about. This system could easily be turned into a DWC and would make maintenance easier. A couple drain/flood cycles before taking nute readings and you could eliminate having to check 12 different buckets. At this point I can't see oxygen deficiency being an issue though. The roots haven't hit the bottom of the first bucket yet, and they are in air/hydroton about 23 hours of the day.

Well, they look worse today but are still growing good. I flushed out the res and filled with plain RO. Will see what happens. I was thinking I'd flush for 24 hours with the plain water, then add nutes to bring it to 100ppm. Should I flush longer? And would it be best to dump the res again or should I just keep the water and nute up REAL SLOW? This sucks!

Still gowing good and new growth appears to look better but it's too soon to tell. Rez came up to 100ppm after a couple floods do to residual in the buckets. Actually works out pretty good. Tomorrow, I'll up to 200ppm and stay there for a day or two. Then ever so slowly up. Will just have to keep a very close eye on my girls.