I don't know if you can update us on your Grey and how he is doing, but it would be nice to know if he's doing any better, and if you have yet to change his diet around, as I must tell you that it's extremely concerning that you said "he sleeps many hours of the day"...that is not at all normal for a baby Grey...
The reason his poop is runny is not due to an infection, it's due to the very high fat-content in the sunflower seeds, as that's all that he eats. All.
I don't know if you are aware of this, but you need to be educated about parrots and Fatty Liver Disease (FLD). The #1 disease that parrots die extremely young from is Fatty Liver Disease caused by an inappropriate diet filled with fat. And usually these birds are eating a diet of mostly seeds, and mostly very fatty seeds such as Sunflower Seeds and Millet. Your Grey is only 2.5 years old, and already his poop is extremely runny, and he's sleeping all day long, which you have to know is not normal. I'm going to go out on a limb and say that the reason that your Grey is only 2.5 years old and is sleeping all day long isn't due to an acute illness, such as an infection or a virus, but rather from Malnutrition, meaning he is not getting nearly the vitamins, minerals, and nutritional content that he needs to be getting every single day. Sunflower seeds contain mostly fat/oil; while they do contain some protein, they do not contain many, if any of the much-needed vitamins, minerals, amino acids, fiber, etc. that your Grey needs to be getting every single day, that we all need every single day...Imagine what would happen if a person only at Sunflower Seeds all day long, every day, and that was it...They would be extremely malnourished, they would have no energy at all, their skin would be discolored, their hair would be thin and brittle, falling out, and they would not feel well at all, having severe stomach and gastrointestinal issues, liver and kidney issues, etc.
I know that you made the statement that "3 vets said he is healthy", but obviously you know that this isn't true, simply based on his droppings along with his lack of energy and the fact that he sleeps all day long and he's still a baby...And forgetting the obvious, I'm going to assume that the 3 vets that told you he was healthy were not at all Avian Specialists...but not only that, they did no tests other than a Fecal Culture testing only for bacterial/fungal infection...So they'd have no way at all to know that he is "healthy", only that he doesn't have a bacterial or fungal infection in his Gastrointestinal Tract...
I know that we had another person from your country not long ago who was able to find a Certified Avian Vet within driving-distance of him. So if you let us know what city/town you live in, we can help you find the closest Avian Specialist to you so that you can get your Grey to him for what is called a "Wellness Exam". This is where the Avian Vet will listen to you while you tell him what has been going-on with your Grey recently, you have to tell them about his runny poop and the fact that he has no energy and sleeps all day long, every day, and also that the only thing that he ever eats and that he has ever eaten has been Sunflower Seeds and that's it...Any Avian Specialist will immediately tell you that you need to completely change his diet around and eliminate the Sunflower Seeds...and they can most-likely advise you of what you need to feed him every day based on what is easily available to you locally. The Avian Specialist may even sell a healthy pellet diet in his office for you to buy...
The the Avian Specialist will do blood-work first, which will rule-out an infection of any kind, and will also show his liver and kidney function, and show whether or not the diet of Sunflower Seeds is causing this lethargy...
Seriously, finding the closest Avian Specialist to you is imperative based on what you are describing, as they will obviously know what is available to you locally and will help you to design a healthy, varied diet that you can feed him every day that will reverse any damage that the Sunflower Seeds and the lack of proper nutrition, vitamins, minerals, etc. have already done. I know in your area you have access to not only lots of fresh vegetables and fruits, but also lots of different "pulses" that are healthy for parrots, like grains, legumes, rice, different healthy seeds, etc. (fruit is full of sugar, so it should also be given sparingly, but way better than Sunflower Seeds, and lots and lots of Veggies is very important, fresh veggies)...So even though you may not be able to buy a commercial pellet diet for parrots you can still provide him with an extremely healthy, daily diet that will not make him very sick and possibly end his life early (I don't know if you can order things online and have them shipped to you, if so then you should be able to get a bagged pellet diet for him every month, along with a healthy and varied bagged seed-mix)...But you need a local Avian Specialist to help you with this, and to educate you about what your Grey needs to be healthy and happy.
