Yeah mine is definitely age related. I have always had a weird head of hair in as much the top layers were naturally blond and silky smooth, the bottom layers was coarser and darker. I also had loads of hair. All you could see was the nice blond stuff, the coatser stuff was hidden. Jump forward to now, the sides of my hair are still blond and smooth (but not as smooth as before) but as I have aged I have lost volume of hair. So now the coarser under layer is now the hair at the back and it has got even coarser and strange textured, it has lost its silky top coat. Its a pain in the arse. I also have seborrheic dermatitis on my scalp - which also got worse as I age. So every other shampoo is with a special shampoo which makes it even dryer.OGX isn't great - I found that it weighed my hair down and didn't help. I'm in a similar position with hair; it used to be my crowning glory too.
I remember reading an article about how your hair changes (texture etc.) due to hormonal changes, as we age. After I crossed my mid-20s, my hair texture became rougher, loses thickness beyond a certain length and my curl pattern changed (it's gotten tighter and not as soft as before)
Sorry for the long boring post. My hair is boring me now. Sick of looking at it. Its a mess.