Hey all. Noticed this spot in my downstairs living room ceiling a couple months ago.

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It's a Cape up in northeast, 35 years old, so these are older popcorn ceilings. Trying to determine if this is water damage? The ceiling isn't soft (stuck a thumbtack in it and it wouldn't go)

but.....

Above it is a bedroom closet, and kneewall, and there appears to be signs of minor water damage from some point. Not sure how old.

I have a few things working against me.

1. We've only lived there since January, and moved in right before all hell broke loose with a terrible winter. Some ice dams, etc.

2. Even though we had a good home inspection, I know those guys don't find everything, and I stupidly didn't take pics while I followed him around.

I don't believe it's an active leak because we've had some serious downpours recently and it hasn't gotten worse, but I'm not sure how to determine the age of water damage, or if this could be just an "age spot" or someone even mentioned from condensation due to that small gap behind it that I need to caulk.

TL;DR - Not soft or crumbly. Should I be worried or buy a quart of Zinsser?