In the past 7 months he has shown some behaviors that he had never had before. The two most important are:
(1) Leash reactivity mainly focused on white dogs. I have been doing training with him on walks to work on this, changed how we attach the leash (various harnesses, flat collar, no prong), changed the routine and it is slightly better but still there
(2) Separation Anxiety - he has always been an anxious dog but has never had any serious SA issues. When we went to the beach in May we had to go back to the room because he was howling like a fool. I just got back from a walk and he was howling. To my knowledge this is the first time he has howled here and I am fairly freaked out.
(3) on a minor note he was more interested in the fireworks the other night than ever before too. I wound up distracting him because he was watching them a little too intensely. He usually pays no attention to any noises
He started his thyroid meds in March and it should be OK now. I understand that can be an issue.
He has always been a whiner when excited and will circle and circle if he thinks he is going somewhere. He is always bummed when you leave and a little too happy to see you return. We have worked on this since day 1. He has never soiled in the house or destroyed anything (while we weren't here to see it 
)
I am thinking of sending him to doggie daycare once a week or so to see if that helps. And/or I might sign up for a class (not sure what) if one is available locally that I can do.
What do you think? Why would these things start now at the age of 4 (well nearly)? What other things might I do?
For the record he is WELL exercised and trained.
Update to say when I left for errands earlier he looked at me, I said see you later and he turned around and went on his bed. So no anxiety at that point