You do get more sensitive to bad lifestyle habits in your 30s, but none of those are normal symptoms attributable to "aging" in your 30s. Really weird when people around this age act like they're just on death's doorstop.
That feels very defeatist, if life only gets worse then I might as well just end it. I prefer to think it's something unexplained and it just shows up more in older people because more things have happened to them so they're more likely to have encountered whatever the cause is.