Could be. There a number of controllable factors that might be at play -- nutrition, water quality/constituents, temps.

It is best by far not to purchase tads and instead start with well established juvenile or older frogs to help minimize variables and thus improve overall outcomes (i.e. get more frogs to live, and live better). The only beneficiary of tad sales is the breeder, who makes a ton of money while having to do nearly no work for it.

 

I’ve had two tadpoles take a really long time to morph. One phyllobates terribilis and one ranitomeya imitator. I used different water composition for them, and their clutch mates did not have the same issue so I chalk it up to genetics in my case. The imitator just left the water and is exceptionally small and on the thinner side, but quite active and chowing down on springtails. I don’t know if it will make it but I will give it a shot.
The terribilis is an interesting one and I considered making a thread on it. It has not grown much or changed colour since leaving the water many months ago

I have frogs that are younger but almost all orange and bigger. Super strange.