Is this a bullfrog or leopard frog tadpole? or maybe something else?

[pacman91]

Hey everyone, new to the forum. Just need some help identifying this species. Did some research and thought he could either be a bullfrog or leopard frog. I've had this tadpole for approximately 5 months. I caught him with about 15 other tadpoles which metamorphosed into frogs within a month, I released them right after. He stood out right away, he grew very slowly and was much smaller. I thought he was albino at first but as he grew I realized he wasn't. He's about 2.5 inches long and seems to be doing very well, I change the water regularly and feed him chopped boiled lettuce. I've been stumped and would be grateful if anyone could help me, thanks!

[GrifTheGreat]

Could be 1 of 3. The third could be a Pickerel Frog. All three species have spotted tads. Bullfrogs are usually darker and larger. Can take 2 years to fully metamorphos. I believe Leopard frogs and Pickerel Frogs metamorphos in less than a year, but I'm no expert.