Follow-up with anyone who cancelled their recurring transactions, assuming they also haven't been attending groups or have communicated that they'd like to leave the training. Having an active recurring donation isn't a requirement for being in the training, but it is a strong indicator of whether or not someone intends to participate. Ask them if they'd like to continue participating in the training, and if not ask for feedback!
If someone recurring donation has been failing for the past two months reach out to let them know about their declined donations and link them to the Managing your Recurring Donations page. This will give them an opportunity to either a) update their donation payment method or b) cancel their donation. It should also give you some indication of whether or not they'd like to continue in the training.