No, it's been like this since a hatchling. It eats and climbs and grows. One of my followers on Instagram brought up that a sweet potato hornworm may have been mixed in with my tomato hornworms. Is this a possibility?
There are black species of hornworms I think...but I've never heard of a cross like you're describing. The sweet potato horn worm and the tomato horn worm are different species but both come from a hawk moth. The sweet potato worm will eat tomato plants sometimes though.