In order to update your prices, create new Plans in Stripe for each that need updating and archive old Plans.
Go to the Stripe dashboard and select a Product that is part of your service. Click "Add Pricing Plan" to create a new plan at the price you want.
Then, go back to the product and archive the old plan by clicking "..." and "Archive pricing plan".
Your Pricing pages will automatically update for the new pricing and customers already subscribed will remain on their current pricing. They will automatically be grandfathered in and only change their price if they change their plan to the new price or cancel and resubscribe. This process will keep you from generating unnecessary products in Stripe and is easy to maintain.