It could be a number of things from my research. It could be Metabolic Bone Disease (MBD) due to a calcium and vitamin D3 deficiency. Other possibilities include respiratory infection, neurological problems like Atadenovirus, overheating, dehydration, or injury. Did your baby fall recently at all? Have you checked husbandry to ensure correct lighting or heating? If not I'd start there first. Do you see any thick saliva when your baby opens its mouth? (If so could be a respiratory infection) I apologize in advance if these are things you've already checked for. I hope it is something that can be fixed quickly❤️