Oh that is awful!! The poor thing! I totally understand why you’d be leery after that ❤️ But yeah, food coloring is a great, non toxic way to tell 😁 you can put it on their backs or heads or wherever but yeah.
I’m not sure how well it would work since they grow so fast but you could try putting different color zip ties on their legs to be able to tell them apart 🥰
You’d just have to watch to be sure it didn’t get too tight but might be a good option if you’re wanting to tell them apart.