Originally Posted by FaeryBee
It sounds as if he has a bacterial infection but I'm glad you are taking Sherlock to an Avian vet because only a professional can give you an accurate diagnosis and treatment plan for his problem.
Just because Sherlock doesn't seem sick "constantly" doesn't mean he isn't actually very ill.
Budgies hide symptoms of illness and the fact that he's exhibiting all signs of illness indicate you need to take this seriously.
Please let us know what you find out after his appointment.
Yes, I assumed that it was a bacterial infection causing him to vomit and have diarrhea, it's just that it is a weird pattern for him to behave normally, droppings normal for 3 days, and then for the next 3 days for him to have diarrhea, vomit and be fluffed up.
I'm gonna take him to the vet, and well... we'll see.