Has anyone else had issues with Tucher? The first few times I had their hefe it was great, but the last few times I've noticed that they were either quite astringent or sour... I've checked the dates on the cans and bottles and they aren't past their drink-by dates.
IMO, Tucher doesn't possess much quality to begin with. Regardless, it sounds like you may have gotten some bottles that suffered during shipment/storage/shelf life. Not sure if Tucher is unpasteurized. Nonetheless, this is not uncommon with a number of German imports, unfortunately -- despite what the "best by" dates might say.
I do not know what Tucher uses for a best by timeframe. It has been my experience that many (most?) German beers that have best by dates utilize a timeframe of 1 year. The good part of this is that you can easily figure the bottled on date. The bad news is that I think it is irresponsible of the breweries/importers to utilize a 1 year timeframe. IMHO, a delicate beer like a hefeweizen should be consumed rather quickly: a few months after bottling and no more than 4-5 months from bottling. If Tucher has a one year timeframe and you are drinking beers that are only 6 months (or so) from the best by date that beer is too old (in my opinion). Cheers!