Hello to everyone from the Jersey Shore!

I have a problem with one of my Columnar Oaks. We planted it
four seasons ago and it was doing great up until last fall. We had “a tree
expert” come take a look at it and he assured us that nothing was wrong with the
tree and it should be as good as new in the spring.
So, the oak did bloom very aggressively about a month ago (my other oaks didn’t
bloom) and now it looks like it’s lagging behind both in height and in foliage.
It’s about a foot and a half shorter than its siblings (I am not too concerned
about it). However, its leaves seem to grow only at the end of the branches (see
photo). Also, there are some strange bumps forming on the branches. Are those
future acorns? Is there anything I can do to help my oak get its fullness back?

Any advice will be greatly appreciated. Thank you very much!

Healthy Oak: