Water them more often, possibly.
Also, how long does it take to drain? The hydroton will take some time to bring the moisture up into the bulk of your medium.
On a side note, when taking pictures of plants grown under LEDs, it is best to introduce so white light (even it you're just using a flashlight) so the plants look their natural color. Sometimes that can lend a clue to what a problem might be.

Thanks for your feed back Grizzman!

I went ahead and set it to flood 4 times a day for 15 minutes. It takes 5 minutes to flood the tubes up to right beneath the wool. The water level will stay there until the pump is off then starts to drain back. The drain takes about 2 minutes to reach the bottom of the pot. So total time in water is about 11 minutes or so. I will take some more pics of the plant, it looks pretty healthy, no discoloration at all, just slumped over.

Look at the stems where they meet the rockwool and see if they look pinched. They will break at the pinched part very easily. If that is the case, what you have is a common bacterial problem that goes by several names like Damping Off, Dampening Off, and Falling Over Disease. All plants get it, not just hydro. It occurs when the bad bacteria in your system or soil, typically Pythium, overwhelm the good bacteria.

Look at your roots to see if they are white or brown. Brown roots indicate root rot, which is yet another name for a Pythium problem. If your root chamber is going six hours between waterings, it will have plenty of time to work its way up to the air temperature. The higher the root zone temp, the faster the Pythium grows. It's tricky, though, because if you keep the rockwool too wet, that will also cause rot.

If it is Pythium, you can try keeping your reservoir and root chamber cooler. You can also try adding beneficial bacteria as a supplement. I put a link below to illustrate.

Here is a link that might be useful: Fungi Perfecti

Thanks a ton for your input, Robbie. I increased the flood times and frequency to 3x a day for 15 minutes. Now the plants are doing much better. Looks like they weren't getting enough nutrients. As for the roots, they look very white and healthy. They started coming through the net pots a few days ago. Even thought things are looking good, I'm wondering if I should increase the time. It takes about 4 minutes to flood the channels up to the root system, so they're in there for about 11 minutes 3x a day. I'm wondering if I should increase that time.

Thoughts?

Attached is an image of the setup.

another pic.

I say go with whatever makes them happy :)

There's a fan in the room that we can't see, right? The seedlings should be gently swaying in the breeze. That will give them strong stems and help prevent falling over,

Yes, there is a fan. Any lighting height suggestions? I'm maintaining a 6 inch height as the plants grow. Will have the lights too low stunt the plants? Here is a most recent image. I have basically have them split, the plants at the end are about a week old, the closer ones (mature ones) are about 2.5 weeks, maybe 3. I should start keeping track.

Keep the lights as close to the plants as possible. With those low output panels, keeping the further away from the plants will cause them to get leggy.

What is the LED light panel output, brand/source? I found some cheap direct-from-China LEDs didn't seem to put out nearly what they advertised...

If they didn't get enough light in the early says after germination, they might be too weak to stand?

Thanks grizzman, I actually learned that lesson early on and moved them real close. That picture is pretty old, I'll post new ones soon.

Nekbet - Those are the quad band LEDs off ebay, they go for 25 bucks. So far, it's looking pretty good especially the cucumbers. They're already flowering and it's been less than 40 days.