Alexandrines are such wonderful birds! You have a real beauty there, thanks for sharing the photo.
Please take all the good advice you have been given concerning diet. No bird can exist on sunflower seeds alone, you can avoid serious health issues by providing your Alex with a healthy diet. Please browse through the diet section and learn, learn, learn. Sunflower seeds should only be given as the occasional treat or not at all. Offer a variety of foods to your little guy, if he turns up his beak at the new foods at first, be patient and keep preparing the vegetables and fruits in different ways, diced, chopped, or shredded, your bird will come around.
What kind of cage does your little friend have? You should take a close look at the bars he's been chewing, it's possible he's chipped off some of the paint and he may have even ingested it. Metal poisoning can cause lethargy and lead to a very ill bird. I'm not trying to alarm you, but it's a possibility you should look into.
Toys should be replaced when they become frayed or chewed to the point of being dangerous. Chewing is great for relieving boredom and providing exercise for your bird. I would choose some new toys with wood pieces, cotton rope or shreddable paper for your bird to try.
Lazy is an accurate description for lots of humans, very seldom for our feathered friends, most of them like to keep busy. Best of luck, please keep us updated with your bird's progress.