I just poured 42 bottles of HB Dunkelweizen down the drain

[MaxStout]

Been using RO for a little over 2 years, and since ditching the tap water, I've only ever used Calcium Chloride, Gypsum, and baking soda (for dark beers). But I've always dumped everything from the boil kettle (tho hops are bagged), so maybe that's why not using nutrients for RO beer wort hasn't caused me any noticeable problems?

I do basically the same. Everything in the BK goes into the FV. I do add the hops directly to the kettle, unless it's more than a few ounces. I rack through a stainless colander to catch some of the hop matter, which helps aerate the wort.

I might look into the ionic zinc and just ditch the nutrients altogether. I can't be sure if over-nutrition is adding off-flavors, but I want to eliminate as many potential factors as I can. I don't have the time or patience to remove one factor, brew, check, remove the next factor, brew, check, ad nauseum. I need to step up my game, change some things. So if it's not needed, out it goes.

Did you taste-test the beer before or at the time you bottled it? Did it have any off flavors then?
That may help pointing to whether it's the fermentation or packaging (bottling) that causes the issue.

Yes, the hydro sample tasted fine just before bottling. Thus, the off-flavor could be developing in the bottles, or it was latent and not noticeable at the time. In any case, bottles are going to get some serious scrubbing and sanitizing before next batch.

 

[Broothru]

I wouldn't leave the bottles soaking in PBW overnight. I don't know why but something precipitates out and leaves a white residue that can be a pain to get off completely. I think it relates to the temperature or perhaps takes time to settle out. Also might be my homemade mix but I use TSP and free and clear All oxy. Usually takes a rag to get it off and you have to pretty much contact every last inch.

Not to mention that the caps may be O2 scavenger caps. Getting them wet, especially even just spritzing them with StarSan prior to capping, might be a source of some obscure chemical reaction with the O2 scavenging media. Maybe that could be the cause of an unintended result? It’s a long shot, but it’s possible if the O2 sequestrent is reacting with the chemistry of the sanitizer.

 

[Broken Crow]

^ I was just thinking about caps... This is a couple of real long-shots, but having read through this, you've covered all the bases I can see except for 2; Are you using a new possibly dodgy batch of caps? Are you using any chemical so-called 'Air-Fresheners" in your bottling area?
Years back when I bought a batch of partially used brewing gear, it included an opened bag of caps...they stank of one of those chemical air-fresheners so I tossed them..dunno how that could have happened, but it did.
Long shot, but just trying to make sure all the bases are covered.

 

[MaxStout]

^ I was just thinking about caps... This is a couple of real long-shots, but having read through this, you've covered all the bases I can see except for 2; Are you using a new possibly dodgy batch of caps? Are you using any chemical so-called 'Air-Fresheners" in your bottling area?
Years back when I bought a batch of partially used brewing gear, it included an opened bag of caps...they stank of one of those chemical air-fresheners so I tossed them..dunno how that could have happened, but it did.
Long shot, but just trying to make sure all the bases are covered.

Interesting point and it reminds me why I try to control my environment, especially when working with the cold side. In warm weather I brew out in the garage over propane. I like to have the door open (and vent combustion gases). But after flame out and before chilling, I shut the door until my chilled wort is safely inside the FV. I bottle indoors, and I close external doors and windows to keep out things that can blow in. I even shut off the ceiling fan out of concern it could stir up dust. I wear a ball cap out of concern some hair might drop in a vessel. I ask my wife not to run the vacuum in the area. And so forth. My wife thinks I'm paranoid, but I always want to remove that risk element.

Bottle caps--I keep them sealed in some airtight container until just before use.

 

[Broken Crow]

Interesting point and it reminds me why I try to control my environment, especially when working with the cold side. In warm weather I brew out in the garage over propane. I like to have the door open (and vent combustion gases). But after flame out and before chilling, I shut the door until my chilled wort is safely inside the FV. I bottle indoors, and I close external doors and windows to keep out things that can blow in. I even shut off the ceiling fan out of concern it could stir up dust. I wear a ball cap out of concern some hair might drop in a vessel. I ask my wife not to run the vacuum in the area. And so forth. My wife thinks I'm paranoid, but I always want to remove that risk element.

Bottle caps--I keep them sealed in some airtight container until just before use.

Right there with you on micro-managing the air in the bottling area and that made me think of one more albeit unlikely and extreme long-shot: When I still bottled, I replaced the overhead flourescent light-bulb with an LED...dunno it the short UV exposure from bottling is enough to have any effect, but I made sure to never find out...Do you have any new lamps?