It is difficult to make a diagnosis over the internet but these sound like seborrheic keratosis. https://www.aad.org/dermatology-a-to-z/diseases-and-treatments/q—t/seborrheic-keratoses
They can be easily mistaken for skin cancer or moles but are completely harmless. They can definitely be scratched off. They tend to get red and inflamed if irritated, which may be what's happening to the sensitive one.
Althought they are harmless, if a lot are changing suddenly (without you scratching them) it might be a good idea to get checked out. It can sometimes be a sign of something else wrong, but this is unlikely. I'd say research about them and make your own decision.
