We are heart-broken

Things are not good. We had really good hatching in our yellow-eyed penguin colonies with a total of 85 chicks. Now we have lost a third of them. Every one of them died younger than 2 weeks old. Five went missing - no idea, 17 died so quickly we could not diagnose, never mind treat them and of the 23 chicks we treated with antibiotics 8 have died anyway. So a total of 30 chicks have died so far and we don't know what else we can do. They are all checked every other day once they reach 5 days old but many died before then. Others were fine on one visit and dead 2 days later. 
The photo shows a 10 day old chick with classic Diphtheria symptoms of loss of feathers on the flippers and upper back, a sunken neck but no plaques in the mouth anymore. Here it is getting it's last dose and it will be ok. We only wish all our chicks had a good outcome as this one.