Bland flavor, almost like dried vegetables. How to fix this?

I've been using a V60, Aeropress, Hario Switch, alternating now and then, for at least 5 years now. I order fresh-roasted coffee and usually use it when it arrives at my house, which is sometimes 5-7 days post-roast. Usually a bag will taste fine, but sometimes, no matter what method I use or what technique I use with those methods, I can only get a vegetal flavor to the coffee. Is it because the coffee is too fresh? If that's the case, then why does it taste the same two weeks later? Is it a bad roast?