How to measure Covid impact by analysing credit card transaction of customer
Do you have some sort of labeled data? 

Otherwise I'd hypothesize that this task is close to impossible since any sort of unsupervised algorithm using anomaly detection would likely have an incredibly low precision since almost all data would be classified as an anomaly during this time.

However, if you were to obtain some labeled data (labeling customers as 'in financial distress' and 'not in financial distress') then you could use some supervised learning algorithm to try to predict whether the unlabeled customers fall in category A or category B. 

Unless you acquire some sort of domain expertise or labeled data, this would be a very hard task.