Have never heard of cleaning behaviour by puffers. I'd be more concerned about aggression: puffers are quite prone to biting one another during aggressive display. This will leave very distinctive circular marks on the body.
They are definately not biting one another. They are eating the the biggest sea lice because they can see them. They are not showing aggression at all. No wounds besides the ones made by the sea lice. The C. irrubescu in the picture looks like it has scars form ringworms, might what to get rid of them.