One plant dying in my 6 plant hydro setup?

Been reading here for a couple months now but haven't had a real reason to post until now. I have a DIY hydro system with 6 plants in it that are on day 24 of flowering. One of them is looking really bad, while the rest are fine. The leaves are drooping badly, it looks as though it isn't getting water or something, even though it is. The crazy part is that the other 5 plants are all fine, which leads me to believe it's not the water. This just started happening yesterday and has gotten much worse since then, in the past 24 hours or so.

They are under a 1000W HPS. PH has been kept at a constant 5.8-6. The res gets changed weekly, with the last change being last Thursday. I use GH nutes (Grow, micro, bloom, koolbloom and floralicious bloom) and have monitored the PPM closely. Nothing has changed at all recently.

Any ideas what is going on here? This sucks.

couple more pics... There is some white moldy looking stuff growing on the top of the rockwool. It's not like the typical stuff, or the other 5. I don't know if you can see from the pic, it's not that great. Also there's a shot from further back.

The leaves at the tops of the buds are staying upright still, so far.

is it possible that this plant is closer to the light or for some reason gets hotter

Thanks for the response. It is in the center of the light's area, but as soon as I noticed it yesterday, I raised the light about 8 inches. There's a fan blowing right across the tops under the light. Temp at the very top of the canopy is about 82-84. Also, the other plant that is right under the light is fine.

Actually, that other plant is not 100% fine, it has some yellowing on the leaves that has started to develop over the past week or so. The problem plant never yellowed though, so I don't see the two as being related.

that pic is wicked rot. pull the plant and hope it doesn't spread to the others. you need to post pics of the whole setup. looks as if you need more air up top and on the bottom.

I agree, looks like rot or mold starting. Does the light hit there? Does the drip system go right there? I had the similar thing, the roots were actually choked out in the res by the others. I had to pull it. Cut it right out.

Sprinkle some baking soda on that white fungus looking stuff.

Do Not water the baking soda into the rez.

The alkalinity should kill the mold.

Rot? What is rotting, you mean that white stuff on the rockwool?

Here's a pic that should pretty much show how the setup works, and one of the canopy so you can see that the adjacent plants are fine. It's a scrog, so they're all touching each other all over the place. It isn't anything that is spreading to the other plants at all, the limp leaves from the problem plant are intertwined with the healthy leaves of the others.

The plants are on 16 in. centers, and there are two rows of three. Three in front and three in back. It's the front center plant that is in trouble.

I watched when the water came on, or listened rather, for the overflow to start flowing. The problem plants site was already flooded properly, just as they all were, so no blockage.

Forgot to describe the system.

The whole thing just fills and drains, right to about half inch from the top of the plant site. The roots are hanging in air, no medium except what's in the 3 in. net pots. It works great, have grown plenty of plants successfully with similar setups.

That's obviously the overflow you see there, which goes right into the res through the clear tube. The black tube is the fill/drain.

The sensor for that thermometer is right up in the canopy.

Looks like I will probably have to pull that plant today as it continues to get more and more droopy. The weird part is the stems are still all strong, just all the leaves are completely lifeless. Still totally green though, no brown or yellow.

I hope you can figure out the cause of this problem.

I am very curious.

It is a problem I have never heard of.

If you pull the plant will you be able to check the roots?

Well I pulled it. It is the strangest thing, the roots appear totally healthy. The look great, feel great, smell normal. There is not clogging. The roots from different plants aren't even touching each other. All of this is great news, as my 5 remaining healthy plants do seem to be actually healthy, and I don't have any problems with my roots, or so it seems.

I am no botanist, but the inside of the plant's branches seem all dried up. It seems like the plant wasn't getting water for some reason. There is really only a little moisture in the very center of the branches. Even down near the trunk it was all dry inside. Maybe it's normal, I really have no reference point on this.

I have no idea at all what happened. The only thing bad that's happened was about 5-6 days ago when I was screwing around with my exhaust system, and while I did, right before I got it back on it was about 92-94F in the room, and must have been well up over 100 in the canopy. That lasted less than an hour. The dead plant was right under the light too, so maybe it just got way too stressed from the heat and never recovered? The other plant that's right under the center of the light seemed to get yellowed leaves, like sunburn or something. They are still really healthy, just yellowed some.

I got pics of the roots, and what was salvaged from the plant. Will post them up in a bit, after I get a few other things done.

Here's the pics, plus a pic of my bountiful harvest.

Good analysis.

Heat and light are problems most growers don't recognize until it's too late.

It's mold. Rockwool is notorious for that. Most growers my self included put something over it. I used to use bright silver duct tape but use pieces of panda poly now. Keeps it from growing and spreading. Mold is a killer. There are a couple of product on the market to kill the mold. Never needed them so Iam not that familiar with them. Next grow cover the pots.

forget the system you have fungus or mold, you were supposed to cover the area around the stem with something to block the light and do the baking soda thing and it might make a recovery.

Have you tried hitting the top of the wool with a sulfur-based fungicide like Safer? That is meant for that kind of mold.