Hmm, you know what? I suspect I left too much headroom in the fermenting bucket. I only had 10 litres of mead in a 30 liter bucket. A couple of samples (very small glasses) I put out weeks ago have started to taste sour, obviously because of exposure to oxygen I'd believe. It's been standing for a couple of weeks in that bucket now post-fermentation. Hmm, is this batch lost?OK, just checking, not everyone understands right away why their yeast rated for 18% won't give them that if they only feed it enough sugar for 12%
If you're sure it's stopped, yeah, I'd rack it off the lees, although "sour" isn't something I'd associate with leaving it on the lees too long. If it doesn't start clearing within a couple weeks or months (by the time you want your carboy back and are either happy with it or have given up on it and want to bottle it or dispose of it) introduce it to some bentonite... it might drop right clear within a few days. Maybe. Them yeasties are tricksy beasts.
I rarely bottle anything from primary, I'm way too much of a klutz and I always stir everything up with the racking cane while futzing around with the bottles, so even if it's a batch that didn't NEED racking before bottling (like a JAO) I usually rack it a week before I want to bottle it if there's any sediment at all. But most of the time, I rack into secondary as soon as the SG stops moving because there's too much headspace in the plastic fermenter and most of my creations need a couple months to clear anyway.
Also, I've had problems with pH-values as you may have seen. Have you had similar problems? What are the causes of too low pH? Is it the honey itself? Or is it all a gamble?
And for my upcoming batch, I'm going to try some better yeasts and nutrient/energizer. For nutrient/energizer, I've read Wyeast Nutrient Blend (the one I used for the current batches) is more for beer and not mead. The ones I've heard mention of when it comes to mead is E.C. Kraus nutrient and energizer (http://www.youtube.com/watch?v=s28auin8k6M) and Fermaid-K from several threads. I'm just curious as to what you're using?