SilverSage nailed it, it's most-likely simply that your bird is fledging...
HOWEVER, if you are not using a cooking/candy thermometer to measure the temperature of the formula you have been feeding it and ensuring that it's between 104-110 degrees F (40.3-43.3 degrees C), then you must worry about either a bacterial or fungal infection in his crop/gastrointestinal tract...Has his crop been emptying over night?
Most people who buy an unweaned baby in your situation/area of the world are not told anything at all about having to feed them formula that is at a certain temperature, and unfortunately we see these posts all the time because the babies are very sick due to too-cold of formula being fed to them..
However, usually these babies are much younger than your baby is at 7 weeks old, and are not fledging...so hopefully that's the issue, but if he doesn't start eating at all today either, or if he suddenly becomes very lethargic, sleeping all the time, vomits, etc., then he's most-likely very sick due to the formula temperature...hopefully that isn't the problem...