Puppy afraid of walks at night???

Hey everyone. We just got word from our vet that we can walk our puppy on sidewalks and around our apartment complex, which she absolutely loves. She’s a 3 month old golden retriever and she started to not like her short walks when it’s dark out. She gets 3 short walks a day, 1 early morning, 1 at around noon and 1 at around 6pm.

She does great on her walks on the weekends during the day and the midday walk but whenever is dark outside she will go potty and then pull the leash to go back home.

Is this normal behavior? Should we be concerned? I am not sure if this might be a fear period although I’ve read that at this age it shouldn’t be an issue. Any advice would be appreciated.

Thanks