Desperate for a solution to my oxidation problems!

My gut feeling is this is happening during bottling because my beers taste great at that point. I know oxidation can happen prior to that and not show up until later, but I don't see any reason recent batches would become oxidized while in the primary carboy for 2 weeks like every other beer.

Background- I've been brewing since 2006 (though some years only a couple batches) and my process hasn't changed. I go from primary fermenter to bottling bucket via an autosiphon, then the bottling bucket to bottles via autosiphon with a bottling wand (no spring) attached. Small volume of water with sugar is boiled 10-15 minutes then added just before siphon. I mean, your standard bottling procedure.

So the last 3 batches, a Saison, IPA, and IPA have gone completely STALE. I mean, they tasted fantastic at bottling and then 2-3 weeks later while carbonating they have gone stale. Oxidized. Significantly darker, weird sweet candy stale caramel flavor... ya know, stale beer. And by darker I mean they've gone from srm 5 to looking like a brown ale. I've used two different autosiphons, and two different sets of tubing. The wand has remained the same but I've inspected it and see no changes. I don't see huge pockets of air inside the siphon. I'm at a total loss here. I use the normal oxygen absorbing caps I've always used and they seem to cap tightly because I get plenty of carbonation. I use to clean with Oxiclean (and rinse out very thoroughly) and sanitize with StarSan, but the last batch I used PBW & StarSan. Bottles are stored between 65-70 to condition.

Really not interested in changing to a kegging setup, though that may be the best solution! I'm just looking for ANY thoughts, no matter how crazy they may be. Maybe someone will see this and happen to know someone who experienced something similar. It's just weird b/c before 4 batches ago, it never happened to me! Many thanks to anyone who has even read this!

My latest batch, an IPA made with 95% Golden Promise, 5% Wheat, 5% Carapils looked like this at bottling:


2 weeks later I open a bottle and looked like this, and tasted stale (and no it's not just "green" beer):

 

Oxidation makes a significant impact on a beer's color (I've seen it over the years many times in commercial beer, but this has also been substantiated by John Palmer). In terms of its flavor, I don't get cardboard. In old IPA's and other similar ales I get more of a weird sweetness, dullness... It's the same flavor I've had from many beers that are farrrr past their bottled on date. I always learned that the cardboardy oxidation flavor only really occurs in very light beers, mostly lagers. In beers of more substance you get more of a caramelly strange sweetness. But I totally agree, how in the world is this happening after just 2-3 weeks when before that it looks great. I mean, I suppose there's a chance this is something else, but this fits with what I've observed in old beer over the last decade.

I definitely don't let it foam to the top, but I never have. Usually it's not foaming, except for the first bottle since the autosiphon kicks up so many bubbles in the first bottle. I can't see infection, though I'm not an expert. I've had infected beer and I'm not getting any sort of sharp, overly dry/cidery, or sour flavors.

color and flavor change in oxidation---- http://forum.northernbrewer.com/viewtopic.php?f=1&t=76157

 

I'd like to make a bottling bucket like that, but I've always just had a separate bucket w/o valve in which I autosiphen a second time out of time into bottles. It's always worked fine, but the bucket w/ spigot would definitely be easier and better.

 

Ok so maybe more than just oxidation going on here.... as I'm opening bottles now I'm getting a big buttery diacetyl aroma which was NOT present 2 weeks ago at bottling. I drank a whole glass of the beer at bottling, and it was amazing. Now it's just a diacetyl bomb, and I'm not even very sensitive to that off-flavor. I'm reading that oxygen introduced at bottling can cause diacetyl precursors to form diacetyl, which would fit my thoughts of bad oxidation here.... Still not thinking infection b/c not getting the dry/cidery/or sour note

 

Yes beer is well carbonated after 2 weeks.

I have dry hopped all the batches that have gone bad. This latest one I dry hopped while there was still some airlock activity to try and push out any added O2. Made a red ale that wasn't dry hopped and it turned out fine. That was my previous batch. But 2 batches before that had this same problem (sans the diacetyl. They only had the very quick staling (2-3 weeks)). So i'm leaning away from equipment infection.

 

Some of the hops were unopened, some were opened from previous use, all kept in freezer and wrapped tightly (though undoubtedly there would be some oxygen introduced to them). The shop I go to sells them in those foil packs you have to cut open... not vac sealed but i imagine purged w/ inert gas, considering it's a fairly big local brewery/homebrew shop (Mother Earth Brew Co).

I do see the trend, and think it's easy to label the dry hops as the culprit, but really? A little oxygen in the dry hops causing a complete staling of the beer in 2-3 weeks after bottling (3-4 weeks after introduction of those dry hops) along with causing possible diacetyl conversion? It just seems like there's gotta be a bigger source, or issue, like a problem with the siphon process or something. Right before all this started happening I had a Saison score 38 in the LA homebrew comp. Was very proud of myself. And just before that a nice hoppy (dry hopped) pale ale that I very much enjoyed (this spans back to last summer though).

Regarding the diacetyl... I really don't think Pediococcus could cause that in 2 weeks at 65-70F conditioning

 

Autosiphon is what I was thinking at first, but this last batch I used both different siphon and tubing. Neither were brand new but they weren't the ones involved in the previous two beers that this happened to either. Neither seemed to be working any differently than they always have.