Three Spot Gourami Having Trouble Swimming

Hi! Bully, my Blue (three spot) gourami has been having trouble swimming for the past two weeks or so. It looks as if she is having trouble with her buoyancy and cannot hang out in the mid-level of the tank with minimal effort like my other gouramis do. She stays at the bottom of the tank and the only time she surfaces is for air and food but even then it looks like she has a bit of difficulty swimming. She is around 3 years old and the only other issue she has is a red bump/growth on her lower lip which appeared when she was 1 year old. I have tried treating her with aq salt, melafix, quarantine, and good old clean tank but it never went away nor did it spread to the other gouramis.

So far to troubleshoot I have tried not feeding for 2-3 days, and lowering the flow of the filter output in case it was too strong (I have a FX4 and cascade).
Tank info:
125gal
Tank mates: 3 krib cichlids, 1 african leaf fish (leopard gourami), 1 pearl gourami, 3 clown loaches, snails, 1 sailfin pleco, 1 clown pleco, 1 gold gourami, and 1 opaline gourami
All of my gouramis, with the exception of the African leaf fish I know are female.
Water levels are tested every 2 weeks to once a month. Levels are all normal. I use the API freshwater test kit (with the drops).
Diet: flakes, bloodworms, algae wafers (for bottom feeders)
Substrate: Caribsea aquarium sand, all live plants.

I have attached a picture of her two weeks ago and some pics of her tonight. Do you guys have any idea of what it could be or anything else I should try?

Edit: I forgot to add that she sometimes will release bubbles from her mouth as she goes back to the bottom.

video of the fish floating/ having trouble swimming?

pictures of the other gouramis?
they might be bullying her.

Edit: It's late so the fish aren't as active but here is the video I got. It doesn't show her swimming issue to the extent that it normally is but it is at least something. I just want to make sure I know what's going on so I can treat it before it's too late.

I did think it could be possible that the others could be bullying her but she is one of my older fish in my tank and has always been dominant. When I first got her I hadn’t realized what a handful she was and unfortunately she ended up killing some other fish in the first tank I had her in. In that sense I do know what gourami aggression looks like. That was in the 35gal before the 125gal.

I do keep a close eye on the fish but haven’t noticed any bullying going on. Piglet (my African leaf fish) just chills most of the day and is most active at night/sunset and I would describe him as “lazy”. Tuna (the opaline) is similar sized but has never showed any signs of aggression with her. Rose the kissing gourami doesn’t seem to pick on anyone either and neither does Sunshine the gold gourami. They all seem to get along. No chasing, aggression, nipping, etc.

I reckon the other blue gourami is bullying her. The weak one might have been top dog a while ago, but she isn't anymore. She might have an internal issue (possible swim bladder problem), or it's old age, maybe both, but she has been demoted to the bottom of the pecking order and is feeling most put out. The gold gourami is also being bullied and is really stressed, but not as much as the blue one is. The dark blue one is strutting around like a proud rooster watching over his girls, except the dark blue one is also a girl.

I would remove the weaker blue and the gold and put them in another tank. The gold and blue seem to get along so they might be ok together.

If you don't have another tank to move them to, add some floating plants like Water Sprite and lower the water level a bit if you can.

Ok, Thanks for the info! I may first try to lower the water level and add water sprite and see if that helps. If it doesn't work I will find a quarantine tank appropriate for their size and let them heal.

I think this is just old age and she is running out of steam.