Yes, garlic is safe for birds, in small amounts.
You may try greatly increasing the humidity in his room to see if that helps, and if not, I would recommend a visit to your avian vet (www.aav.org/vet-lookup) .
Things to avoid: anything that is consider human 'junk food' should be treated the same for birds. Avocado, chocolate (the darker the increased toxicity), alcohol are all toxic.
Here are some websites that will give you more comprehensive lists:
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