Sudden wilting of Sour Diesel

Help!
Four weeks into flowering my Sour Diesel has suddenly wilted! I have never grown this strain before so I don't know if it is sick or going into bud set. I have heard some strains of sativas will shed their leaves as flowers mature. I hope this is the case here.
In the background you can see the still healthy OG Kush. It shows no signs of any problems but I am worried, plus I don't want to lose my SD.

Setup is DWC with 4 airstones. Water temp 65F. pH is 5.5 - 5.8.. Tiger Bloom at 75%. Lights are cfl.

I sure hope somone has seen this before and can tell what to do, or at least tell me what is happening here.
Oh yes, I did examine the roots--no smell or discoloration.
I changed the water, wrung my hands, threw out a prayer to the pot gods, ran out of ideas.

*Before taking this advice....I am very new to growing.*

I think we need more info on your light setup. Are the CFLs only on top...do you have some on the sides...etc. I ask because I'm using CFLs and the bottom foilage dropped off because they weren't getting light. Plants are fine...just less bushy in the undercarriage My lights are only on top of the plants due to cabinet restrictions.

Lights are on top as well as on the sides. I think it is too late any way. As of this posting, the plant is totally wilted. Leaves are green but totally lacking tugor. Calyxes are now also wilted. RIP Sour Diesel

so youre running two strains on one setup right? if so could it just be the plants being picky and requiring diff water or nutes?

cause it looks like overwatering

It sounds like you have done everything and checked everything. It really doesn't make sense. A full res change with lots of air is all that I can think of. Good luck

Looks like over watering to me also, but what is your canopy temp?
Good air flow?
I'm on my second Diesel now, and I've found the Diesels to be a little less tolerant of higher temps like my others.

Yes, it is dead as a hammer this morning. OG Kush is still fine. One of Life's great mysteries, I suppose. Thanks very much to all who posted!
I don't think it was overwatering. It was DWC! lol

Heat is prob what killed it. Or u let it run out of water.

Sent from my SCH-I545

No it NEVER ran out of water or exceeded 80 F. The other plant in the chamber is doing great.

That's crazy.

Sent from my SCH-I545

is the air pump on? take the lights away, cool the room to around 65 to protect any cells and what little water they have in them. replace the water with plain water at the right ph. tiger bloom is great untill you over do it!!