It is not dirt. They look like dark water stains from roof leaks. Get an expert who can check for mold and also put a moisture meter on the stains to check for active roof leaks. The expert can lift the insulation and check the drywall ceiling. If you don’t see water stains on the interior ceilings and the roof sheathing is dry chances are they are from old roof leaks. Has the roof been replaced recently? Check google earth for historical photos, which may help, in addition to checking for city permits.

@dianeski The interior ceiling has no water stains. The roof hasnt been replaced and theres no permits with the city. Based on @Stax advice, I ended up getting a mold inspector to come and test tomorrow. A neighbor did say that he has roof leaks that the HOA isnt helping take care of, so it could be that. I figure worst case I end up having a roofer patch up around there, as long as the stains haven't gotten moldy.

Needs a new roof if it’s “never” had one.

If it's mold: 1) does it matter? and 2) getting rid of it, without fixing what caused it, is a waste of money - it'll come back. Maybe attic isn't well-ventilated along with poor air-sealing from below.

Does it have an exhaust fan from say a bathroom venting into the attic? If so it is likely the cause of mold in the absence of leaks.

@Seabornman my main concern is identifying if it mold because like you said if the issues causing it arent addressed they will only get worse by the time I choose to sell and even if it doesnt really matter to me if the problems not that serious now, it could be a problem to any future lender for a prospective buyer.

@lyfia Ill check today when im up there with the inspector