these might have been caused by affix adjustments to +VIT series. most likely, they are. I'll try to avoid morphing as often as I can. currently, there's no need to update affix data. but try keeping more items at Gill. perhaps some items will morph into something better if there will be changes in affixes.
also note that items from previous versions stored at Gill arent updated (thats why quest uniques dont morph when stored by her) and their data is refreshed only after you take them out and restart the game.
about AC on items, u shouldnt be bothered. numbers are just numbers. it's how you feel playing the game that actually matters. make sure you check those excel tables I uploaded in AC guide, they will be really helpful I believe =)
Sorry about the morphing buddy but you know Diablo-based game has this feature. you just cant change something without a flaw (or a change) popping out somewhere else. It's a damn random thing