Seeing a discrepancy between your scores from different credit reporting agencies is very common and not something to immediately worry about. The most likely reasons for a discrepancy are as follows
A different scoring model was used - Your Truebill credit score is calculated using your Experian credit report and the Vantage 3.0 scoring model. The Vantage 3.0 model was created by Experian, Equifax and Transunion but is not the only scoring model used. In fact there are many different scoring models used by creditors to determine your credit worthiness and each weighs factors slightly differently depending on their intended use.
Your lenders may not report to all credit agencies - Not all lenders send data to all credit agencies. That can result inconsistent data being used to calculate your score.
Timing - Not all lenders will update all credit agencies at the same time. There maybe some variation in terms of when different agencies receive your data and that can also result in differing scores.