I appreciate ur concern.
Trust me he is perfectly all right and very very active,
What I have observed and learnt that birds , specially parrots , don't eat a thing which is not good for them, I have experienced this. The Roky visits out side once a week, fly's around the house, sits on different trees and after a ten to 15 minutes visit we call him and he flys back. During his visit he doesn't eat every thing.
The birds who live on their own in open world they filter the food them selve, nature has put a filter inside them
"Regular" tea isn't good for birds or any animals really because of the caffine...and sugar..and the milk blah blah blah.
But when I had Jonesy ( a Goffin 'too) he too enjoyed a couple sips of my tea,but I drank decaf with no sugar or milk..UNTIL after he had his share
B&G Macaw, Galah, 5 cockatiels, 50 billion and a half budgies. We breed and do rescue. Too many to list each individual's name and age etc, but they are each individuals and loved dearly.
Herbal tea is just fine(in moderation) too. Can even be quite good for them.
The milk and high sugar are not great for birds though. I'm sure he likes the taste a lot, but he cannot digest the lactose in the milk.
Just like kids, some times they eat something that is very tasty that isn't the best for them(like sweets or chips for kids). A little bit now and again won't do too much damage, but his stomach could be upset if you give too much or too often.