My pet budgie has been puffed up all day for 3 weeks and he has vent feathers all brown and has poo sticking sometimes. Now as the third week he has no pop sticking on his vent feathers but his vent feathers are still brown not like my other two and is puffed up all of the day. Those are the only symptoms I see, I can not go to the vent because of COVID.
Sometimes during moulting budgies behave so off and calm. They can spend days puffed on one spot. But, sometimes that can show us that something is wrong with your budgie bird. If you want to be 100% sure you need to take your Bird to the Vet. There is a video about sick bird symptoms you can check it out. Anyway, give your budgie a lot of fruits and vegetables to gain his strength.