Without knowing which salsa recipe you used - and hopefully it was one approved for canning - it is difficult to identify what the problem may be. Could you post the recipe please or link to it?

But it is true that some spices can intensity or even turn bitter during shelf storage. That is especially true for fresh spices vs. dried.

Yes you can adjust some flavors after opening the jars. Sometimes a bit of sugar will off-set bitterness.

Dave

I can't find the exact recipe--I've used a number of different ones this fall and have since found one I liked better, so I didn't keep track of this first one. It had lime juice to acidify it, and fresh cilantro...and it was a canning recipe. I switched to vinegar after this batch and didn't add cilantro, so I'm hoping the next batch tastes better.

Thank you!