My Centennials have done the same thing. They were the first up and grew strong for a few weeks then just kind of stopped growing. My Mt. Hood 5 feet away started slower but is now twice the height of the Centennial. The Mt. Hood is now about 8' tall.
Uff Da Picobrewery
Primary: Arrogant Bastard Clone, Pumpkin Ale
Kegged: Marble Red Clone, Cream Ale, PilsAle, Cider
Bottled: Yule Gruit, Unhallowed BGSA (10-10-10), Nymphetamine Barleywine (999)