If you use the fitday log to check how many calories you're actually eating, that may give you some insights.
Aging plays a part - few people have the same metabolism they had when they were younger! Also, your skin changes as you get older - I've noticed more skin tags as I age and (gasp) the first 'liver spot'!
OK, so I couldn't predict those things, or when they'd appear. They don't even run in my family. But a dermatologist and my own family doctor said, basically, 'Things change as you age!' Always mention them to your own doctor anyway. I'd be interested if that can be easily changed (without side effects).