Using Photoshop CS6 to Edit Images in iStopmotion3 causing issues

I’m creating an animation with iStopmotion3, and I’ve been using photoshop cs6 to edit frames. This has been working fine for me, except for now. When I now use photoshop to edit frames, it darkens them a lot. I don’t even have to edit them; just opening the frame in photoshop, and then saving it (as a .png, not changing anything), and the frame becomes much darker in iStopmotion3. This hasn’t happened before, and I haven’t changed anything about how I’m working. Any ideas?

It sounds like a color management issue. Maybe you switch your default Color Working Space in PhotoShop?