At least one of them was definitely a spammer (because I remember seeing spam on your thread and zapping the perpetrator).
Most mornings (often between 3am and 4am) a new poster appears, always with an automatically-generated username consisting of random letters. That member (or, rather, the computer which is pretending to be a new member) then floods all recent threads with spam.
The late-night moderators (such as me) or the early-rising ones usually ban the spammer fairly quickly.