Yes, you’ll need to exclude the custom audience (e.g., IG engagers) separately in each lookalike ad set where you want the exclusion to apply.
Exclusions are applied at the ad set level in Meta Ads Manager. So even if two ad sets use the same lookalike source, each one operates independently when it comes to exclusions. If you don’t manually exclude the custom audience in both ad sets, Meta could still serve your ads to those IG engagers through the lookalike targeting.
What To Do
- Go to each lookalike ad set
- Under the “Audience” section, scroll to Exclusion
- Add the custom audience you want to exclude (e.g., IG Engagers 30 Days)
- Be consistent with exclusions across ad sets—especially if you're trying to avoid audience overlap or retargeting people who've already interacted with your brand.