I changed the discount in my auto-charging subscription rule, but my subscriptions are still on the old discount. How do I update their discount?

In case you updated the subscription discount in your subscription rules, what you could do is enable the feature to apply discounts from your subscription rules on price change propagations, which you can find by going to Seal Subscriptions > Settings > General settings > Auto-charging subscriptions > Price change propagation > Apply subscription discounts on each price change propagation.

Once that feature is enabled, you can then go ahead and click the “Trigger update” button under “Refresh product prices now”, which will cause the system to start syncing the product prices of your subscriptions, but also apply the latest discount from your auto-charging subscription rules! This way, you can bulk edit the prices on subscriptions in your shop.

The other alternative to this would be to create a product swap in Seal Subscriptions > Automations > Product Swaps which will replace product A with the same product A. But when configuring this product swap, you also set a custom price in it for the newly added product. This way, you can update the price of the product in your subscriptions in bulk.