Why are some of my new hybrid tea blooms very small and deformed?
They are second year bare roots.
You planted them this year or last year?
Young plants not established don't have the resources (a strong root system, canes containing a lot of stored carbohydrates) to produce their best flowers, just like a 21 year old man is a lot stronger physically than he was when he was three.
Patience! This assuming the roses are getting regular water and are in decent soil and are getting a goodly amount of direct sunlight (6 hrs) daily during their growing season.
One thing exclusive of plant establishment is Thrips--are the edges of the petals brown? If you shake a flower over a white piece of paper you may see tiny brown insects--those are Thrips, a rasping insect that can ruin flowers. The other thing is extremes of weather--a forming bud can be damaged by a sudden near-frost or a nasty heat wave. But the other stuff first.
If they were hit by a cold snap during formation, that can do it. Also, if you mean strange green centers, that's called proliferation (there are threads with photos), and it happens in some varieties in the spring, usually on the very first buds to form.