I've noticed lately that my stats in battlegrounds are bugged. For example, outside of BGs my base stamina is 10k, but in BGs its 9k. Now keep in mind, 10k is the standard unboosted base stamina you will have if you don't increase it via attributes/items/food/etc. My Magicka is also goes down by 3k. Also, my HP only goes up by 2.5k in BGs. A friend of mine is actually getting LESS HP in BGs then outside.
Now, just to eliminate a few things:
1) Yes I know there is no CP in BGs, and no, CP doesn't affect your Max Stats directly.
2) No, this is not the Crown Poison Bug, I made sure I didn't have any poisons slotted when I ate my food
3)I also tried eating a variety of different foods but I'm still missing Max Stats. I also took off all my gear, and I've done everything else I can think of.