Day 8: Differences increase?

Day 8: my caterpillars are looking more and more different each day. It's almost like they're not the same species!?
But they eat the same food... and what are the odds that two moths should lay eggs at the same time in the same place on the same leaf (even though they were captured in a container) and that these eggs would hatch at the same time... and... I don't know. There must be a better explanation. Any suggestions? Let me know.