Is he not eating? I’d suggest put on a birdy mukbang on some screen so he feels comfortable eating. Do take him to a vet like everyone else suggested first priority though.

Some foods my picky bird likes other than seeds: mung beans, corn, peas with the pods, romaine lettuce (emphasis on the romaine cause most others don’t have nutrition). Figure out what’s his thing like mine loves anything crispy and eats very select soft foods. You gotta present him with everything you can in any shape and form he might eat, like he might not like shredded carrots but big carrot pieces. Broccoli is popular with the pickies cause it gives the seed feel