Left eye balding and abnormal poop

Dear TB forum members!

What a great place this is. I introduced our dear budgie Robert in a post some days ago, but will have to turn to you again for some advise on our little friend.

We're afraid Robert has some (hidden) health issue. Naturally, as we only have him now for close to two weeks, we don't really know yet what is his "normal" behavior... But I can say, that in the first three days that we had him, he showed some remarkable aliveness and was quite investigative and vocal for a 'new' bird. We were surprised in fact by how easy he seemed to adjust to his new home.

However, I think that on the night of the third to fourth day (which was suddenly cold) he might have contracted something, due to also maybe lowered immune system because of stress. Since that night, we feel he became less inquisitive, in principle he does not "look" like a sick bird, but he gave us the feeling he is hiding something. He is less vocal, sits more still. More passive. Initially he was interested in investigating his swing, flying towards it, now he prefers to leave it alone. He appreciates us communicating with him, but he is more to himself. He is not fluffed up though, and sleeps on his highest perch. His eating behavior seems normal, and he also lets us feeding him water and seeds by holding his cups close to him.

However, now we have started to see some more indications that indeed something might be wrong with him. Let me include two pictures:

We have grit on the ground, but with some paper we were able to see something is off with his poop:

This is from one night, so some normal (at least they look normal to me), but then suddenly also some diarrhea.

Also, since yesterday we noticed that Robert's left eye is balding slightly:

So these things quite alarm us.

Perhaps there are some forum member who could shed some more light on his condition? Anyway we got a phone number of a local avian vet, so that is good. We will contact her on Monday. But your opinion would also be very much appreciated.

Thanks a lot.

-Willem