Something's gone wrong - slightly sour and/or bitter taste

I just recently racked five meads (three one gallon batches and two 5 gal batches) I started last spring/summer at different points (may, june, july, and august). They had all been neglected for a while and were over due for their second or third racking. The last racking we did was over 4 months ago (February) and they were tasty but young at that point. After this last rack they are all a bit sour, dry, and not very alcoholic tasting/ "flat" (although we haven't been taking specific gravity).

This has never happened before. They don't taste really sour or acidic like some posts have claimed but they aren't very good... I'm not sure what to next. Other possible variables are:
1) we moved to a moister colder climate in august (so the move might have been too much)
2) they've been moved into a basement that is colder (and moister) than the place we stored mead in the past.
3) they have been getting much less frequent attention since we moved

I think it's a combination of the yeast not fermenting much in the colder environment and something introduced into the whole group. If something's been introduced, is there anything we can do to restore the good flavor? Any other opinions? Any suggestions?? You're help is very much appreciated.
Thanks ???

I'll post the recipe and procedures but we didn't take the specific gravity.

For example our cherry rose mead recipe is as follows:
1/2 gal cherries seeded and smashed
small bowl of rose petals
6 lemons Juice and a little peel
1 gal starthistle honey
champagne yeast
pinch of pectic enzyme
good vibes

Procedure:
-Batch started around July 20th
-let that sit in the bucket for about 5 days
-strained all fruit and petals and racked into carboy around july 25th
-1st racking august 8th (a bit early) (temperature was around 70-80 degrees until we moved locations at the end of august to about 50-60 degrees, may have dropped down to high 40's in winter months.)
-2nd racking 12/18 (a little late, usually we rack every three months but as I said life was crazy and meads got neglected ) tasted young and a little bitter from lemon peel but otherwise fine.
-3rd racking 5/16 (tasted sour, a little bitter, but young, as if it hadn't been fermenting much). Basement where the meads were kept was very moist, with possible molds in air... but airlocks were still on etc. however, something may have got introduced into the mead at this point.

This is pretty much all the info I have. Any ideas? thanks.

and thanks for the welcome.