Hi, I can help you with your question today.
The changes that you have noticed with him are very concerning.
Inappetence and lethargy are fairly non-specific though.
Can you lift his lip and look at his gums? What color are they?
OK. Is he having any increased effort to breathe?
OK. Has he had any vomiting or diarrhea?
Could he have gotten into the garbage, chewed up a toy, etc?
Excellent. Have you given any people food? Any diet changes recently?
Since you were at the seaside, we can see unusual ingestions (such as sand) or water borne parasites like giardia.
I recommend having him evaluated by your local vet. I would start with a physical exam, stool sample to look for parasites, and x-ray to look for foreign material or evidence of obstruction.
You're very welcome. Please let me know if you have further questions. I am happy to continue until I provide the service that you seek.
Great. Please feel free to send any questions for second opinion to me! I will try to contact you in a few days to see how he is feeling.
Again, you're welcome :)