As long as the campaign is active, adding products to the target collection (vendor, product type, tag) or removing products from it will not affect anything (prices and discounts will not change).

The app changes the prices of products/variants only at the time of activation or deactivation. It does not update prices in real time.

If you still want to update prices for these products, then you need to Refresh the campaign. The app will add a discount to new products according to the targets and remove the discount (return the previous prices) from products that have left the targets.