Looks like bottom sitting to me, have they spent long periods of time like this?
It could be the water quality causing this issue. Goldfish let off a lot of waste, so when in a small space, that waste builds up and can become harmful. You can either get a water quality kit and test it at home or you could take a sample to a pet store, they often test it for free, so let us know the results.
May I ask how often and how much do you do water changes? And also how often do you clean the filter media? How often and how much of the filter media do you change?
I re call you had this tank in March? (Judging from your last post). It's possible that spending time in the small tank has stunted the fish, which means they're growth can be slowed, or in some situations when moved to a larger tank, the fish can have growth spurts, so be prepared for either eventuality
As they are single tailed these fish will eventually need a pond when they are big enough, but in the mean time, I would suggest you look for a larger tank, something around 4 foot should be ideal for these two as a temporary
home. Get yourself a decent filter too, an external one will be best as they hold more media.
You can look after them until they're big enough for a pond
We can help you with setting the tank up and cycling it properly so you have good water quality before moving the fish. I know this is a lot to take on board, so take your time to read it and please ask away if you have further questions.
You could always look for someone with a pond to re-home them if you're un able to organise a bigger tank
I've been in the same situation, so I understand, I had a goldfish in a tank too small, I upgraded her to a larger tank in January and now I'm caring for her until she's big enough for a pond
Hope the fish are okay, let us know how they're doing.
I hope what I've written makes sense! Sorry for rambling XD