It happens quite a bit when people first start VLCDs, actually.

Nothing too much to worry about. It's likely to be due in part to a drop in Vitamin K (if you had a healthy-ish diet with lots of green veg before starting, your intake of Vit K is likely to be less on a meal replacement diet than it was before). Your body will adjust to the relative drop over the next couple of weeks (there's sufficient Vit K in the packets). You might find you bruise easily too for a while. In addition, you're likely to be brushing your teeth a bit harder than usual at the moment because of how ketosis makes your mouth feel, if that makes sense? That sensation also passes as you get used to it. If it continues past a couple of weeks it's worth consulting your dentist but it'll probably sort itself out fairly quickly.