How to improve a CNN without changing the architecture?
Are you in fact using the same architecture as they are? If not that could potentially be the problem.

Otherwise, are you using the same trainings protocol as they, i.e. optimizer, learning rate, learning rate schedule, batch size, preprocessing, weight initialization, number of training epochs? Depending on the size of your model and the amount of training data, 10 epochs might not be enough to judge about your models performance.

Can you link the paper?