u/ExcuseAppropriate862

So I posted on here a couple days ago bout my oscar. I listened to everyone's advice. I added botanicals, I removed some limestone, increased oxygen etc. He just seems to be getting worse. I constantly monitor my parameters and do a water change accordingly. He's pale. Kinda has white film over an eye and seems to be gasping for air now. I have ordered api general cure to see if that'll help as my little oscar has white stringy poop. He has also taken a turn. They both refuse food but it's just them. All my other fish seem happy and healthy. Im at a lost on what to do. Any advice would be hugely appreciated.

Almost been a week!!!

Little bit of context. My oscar has been constantly laying on the bottom. While I know they are drama queens. It seems to be getting worse. My tank parameters are 0 ppm ammonia, 0 ppm nitrite and 5.0 ppm nitrate. I spoke to a friend and he advised me it could be oxygen so I pointed my fliter output at the surface as like a kind of waterfall plus I have my airstone on. He still comes up to the surface for food but as stated it seems he spend more and more time on the bottom. From the video you can see he is still lively but its just concerning