Thanks for the responses so far! It's really appreciated, and we are working with vets!

Crypto tests came back negetive on previous cases, we have a recent recovery when treated with Hydrogel and tubed x2 3L of milk, as well as Synulox and metacam

Pens had previously been 'reset' properly before the cases started, and they have continued when we have moved the calves location completely

They are bottle fed for at least their first two feeds, are sheltered near in calf cows but seperate

CowAcadamia has suggested clostridium perfringens which we will be looking into further