After collecting all the data we have, there are only 6 Ds and 15 Cs in the dataset. That is almost impossible to train a machine learning model.
Data Size: The size of your dataset is relatively small. Machine learning models generally perform better with larger datasets because they have more examples from which to learn. Small datasets can lead to overfitting, where a model learns the training data so well that it performs poorly on unseen data.
Class Imbalance: The dataset has a class imbalance.