Please help - off flavor need to identify

Brewed three lagers in January. Lagered a month, then kegged. They were all delicious, for about a month. Now, they are hard to drink.

Let me describe the off-flavor:
Whereas all three leaned to “malty” beers, now they taste more “watery” than malty, as if the sugars have thinned. There is a tartness (not quite a sourness) in the flavor that lingers, unpleasantly. A “minerally” flavor is there too, and in the aftertaste.

My thoughts are: bacterial contamination, which occurred prior to kegging (or even fermenting) since the same off-flavor is in all three kegs. Your thoughts? Have I overlooked anything? I am currently prepping to buy new beer lines, autosiphon, and siphon tubing.

It sounds like brettanomyces to me - has there been increased carbonation? Can you degas a sample, measure with hydrometer, and see if there’s a gravity drop?

I’m assuming you’ve kept the kegs refrigerated. This is odd, as usually fridge temperatures will keep most things from growing for either yeast or bacteria. However, I have a vial of brett anomala from ECY that’s been active in my fridge, so it’s not out of the question.

I did keep kegs cold. Great idea on re-measuring w hydrometer! Will do.

I suppose its possible the “when” of contamination was post-tapping (bacteria can creep into faucet and up thru lines into kegs; but doubt that happened to all three kegs. Guessin was pre-kegging when occurred

Good chance of it… I’m guessing you re-used the yeast? Something could have crept into the culture that worked slowly at fridge temps.

I think you’re on the right track by replacing the soft plastics. If it’s a wild yeast or bacteria, star-san will definitely kill it. Also, heat works great if you can submerge the hoses and what not in a bath of 180F water for 10 minutes or so. Wouldn’t try that with glass or PET, but I like to fill my primary buckets with 180F water/oxy for awhile after they’ve had brett or bacteria in them. So far (knock on wood) no cross-contamination…

I didnt re-use yeast. Used two packs dry yeast for each normal-strength lager (1.049 OG).

I will replace some siphoning equipment, boil my kettle spigot, etc. prior to next batch.