Amla starts off lighter and gradually turns darker as it ages or is exposed to air. It does not mean the quality is diminished as it ages. In fact, some people prefer the taste of aged Amla, as the freshest Amla tastes the strongest, but mellows over time.
I doubt that the quality really holds up. Darkening is a classic sign of oxidation.
This study confirmed the variability of baobab with different origins
I'm considering switching back to amla for this reason. Amla is cheaper due to its potency. While I don't like the taste of amla, it's easily tolerable provided I know why I'm taking it.
CONCLUSION: This randomized double-blind, placebo-controlled clinical trial demonstrated that Amla could reduce frequencies of heartburn and regurgitation and improve heartburn and regurgitation severity in patients with NERD.
Is there anything it can't do? I have noted, however, that larger doses cause nausea for me. That is, 3 or more grams on an empty stomach. I just vomited after taking 7.5 grams before my meal, but I have not yet established the causal link. It is the largest amount I've ever taken at one time. I suspect that it may have contributed significantly, but that it was also one out of half a dozen factors.