Hello guest! Are you an Apistogramma enthusiast? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's a great place for Apisto enthusiasts to meet online. Once you join you'll be able to post messages, upload pictures of your fish and tanks and have a great time with other Apisto enthusiasts. Sign up today!
That's a common occurence in such domestic breeds. It's indeed a runt with a bad genetic combination. Likely it doesn't have a fully working swim bladder to start with. There's nothing you can do. I'd probably euthanize sooner or later, once it becomes apparent the fish is suffering.
This is what you get from generations of line- and inbreeding.