Growth looks good, but how long hAs the stem been that way? It almost looks like the beginning of stem rot, but I may be wrong.
your stem/stalk has me seriously concerned...
Yeah, I'm definitely keeping a close eye on it... As far as I know the stem has always been that way though. It just keeps getting thicker and greener above the pinch so it's looking more exaggerated over time. There is definitely root matter above my rockwool, just below the pinch -- I kept trying to tell myself that maybe the section is semi-normal and it's usually just below ground so it doesn't look so frightening, but I kindof doubt that theory. It seems a bit weird that one section of the stem wouldn't grow with the rest. Hrrm.
If it does turn out to be stem rot, what should I do about it? My rock-wool cube was a bit damp for a few days about a week or two ago, but I wouldn't think that would be enough to cause rot. It has been relatively dry ever since, especially since I moved her up towards the light a bit more (no more moist than it should be anyway).
EDIT: By the way, the texture of the pinched section is dry, hard and a bit flaky.
EDIT 2: Just did a little research, and I didn't find any pictures of stems with rot that came down to a pinch like mine. They all look full sized and they have brown or white stuff (mold/fungus) on them, and I get the impression that they're not too solid eventually. By the looks of it, I'd say it's either a VERY advanced stem rot (in which case I'm surprised my plant is still alive and doing so well), or it's something else.
EDIT 3: I suppose another option is that the stem *was* affected by rot early on while the rock-wool was wet, and now it's healing. I can't imagine it would still be rotting in that section if it's not even touching the cube.
EDIT 4: Here is a repost of a picture from a week ago (the only other good picture I have of the stem). In this picture taken a couple days before defoliation, the stem does look a bit strange. It is fair to say that it looks way worse now, but I feel like it hasn't degraded further in the past few days. I'll start taking daily pictures of it to make sure, as the plant is growing so fast it's tough to judge based on memory alone.
EDIT 5: So I've come to the conclusion that it most definitely is root rot (or at least was). I took off the bit of dry flaky stuff (turned out to be an old stem husk -- plants shed too, you know!) and found a dark/blackish section of stem. I was able to scrape it off fairly easily with the back of my fingernail. Here's a picture:
My research tells me that the condition is pretty much untreatable. If the plant "recovers" it still won't yield as much as it otherwise would, so I'm contemplating just straight up chopping her down and starting over. If I do this, I'll have to make sure I disinfect / sterilize everything that may have been exposed to the fungus. Grr. I'll give her a few more days and we'll see.
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. I like my new low-maintenance flush schedule, but I have to keep in mind that at this point in my previous grow I was increasing nutrient level virtually every flush I performed (every 4-5 days).
. Goodjob on the first harvest man.
. It's pretty cool to see the contrast between soil and hydro systems. At this scale it becomes really obvious that plants in each system grow very differently. I like how you put that... you're dirt, I'm water. Different specialties, similar desires and results. Good stuff 
