Is it true canaries stop singing at age 5? How to keep them singing?

How much a bird sings varies greatly on the individual bird so it would be impossible to tell you when he will sing again or not. Making sure he is on a balanced diet, and having your vet take a look to make sure there aren't any lasting health issues caused by the malnutrition earlier is best to make sure Ringo is still healthy and happy.

Thanks for reaching out about Ringo. He should not be in the vicinity of any aerosols or burning candles, near the kitchen or where fumes are. Canaries were originally used in the coal mines to warn miners of dangerous fumes, as they are much more sensitive. Wearing cologne or perfume should be acceptable, within limits, and after the scent has settled. Canaries can live 15-20 years, if healthy, proper diet and good genetics. As for loosing their voice after 5 years, no scientific evidence could be found to support this. Good luck.

A common cause of "drooling" in birds is a yeast infection. Consider a recheck with your veterinarian or an experienced avian veterinarian. Submit a sample of the drooling for analysis and culture. This may diagnose a yeast or bacterial infection which can then be treated appropriately. It is not uncommon for a canary to stop singing when ill. He may start up again once he recovers.

That is pretty young for a canary and if they are not in a well-ventilated area, it certainly could be a potential causes. Cooking fumes, especially from products such as Teflon pans, can be toxic to birds, so moving the birds to an area that is better ventilated and away from the cooking area/vents is a good idea. Keeping the environment around your birds clean and dust-free can also help them stay healthier.

This may be "normal" for Ringo. Molt times are only estimations based on 'most' birds. Stress, illness or diet can play large roles in molting. You can have him examined by your veterinarian to diagnose any illness or to confirm good health. Confirm proper environmental parameters and diet. There is no way of determining when he will begin singing again.

I've not heard of food alone aiding singing, but the right nutrition can definitely help Ringo feel healthy enough to want to sing. Spending time with him, making sure he's getting enough light, and providing fun toys and other enrichment can also help encourage him as well.

This definitely sounds like something other than molting, especially if he's very lethargic or showing other signs of illness. I would bring him into your vet for a complete exam and even possible bloodwork to rule out issues such as parasites, infections, illnesses or even nutritional deficiencies that may be causing it. Making sure to keep him warm with easy access to a balanced diet and water may help some until you can be seen by your vet.