You have my empathies. I spent the first half of this year nursing / providing palliative care fish of 4.5+ and 5+ years with curved spines, bent tails, etc. (in my case, they were harlequin rasboras and x-ray tetras), and have also had a few young cardinal tetras with potential dropsy. Whether or not it's TB will never be definitively known without a post-mortem or diagnostic test. As for whether it's dropsy, it can be difficult to tell whether the scales are protruding on a small fish. On a goldfish, there's no doubt; on a cardinal tetra (similar size to your zebra danio), it was only evident by switching off the filter and shining a torch from various angles, and not even conclusive whether all the scales were protruding. Looking closely at the photo, though, I think the scales are protruding under the belly. Protruding scales do tend to be the end-stage of dropsy.
You have a few options - you could leave the fish where it is as it's behaving fine and has the benefit of its shoal-mates (but, if it's TB, the others may become affected albeit they may well be already having been in this fish's presence) OR you could isolate this fish in a quarantine tank and treat for potential bacterial infection to see if it cures the problem and possibly even keep it there afterwards if s/he seems unperturbed by being on her/his own (and thereby reducing any risk to the others) OR you could take it out temporarily for a daily Epsom salt bath for up to 20 minutes to see if that reduces the bloating factor.
Which of these is best may come down to your hunch, the personality of the individual fish, and how it responds to capture (willingly/'refusingly') and being moved into an isolation tank. [Eg 1: one of my elderly fish was quite sociable with the rest and quite blind but seemed to rely on finding his way round by nudging his tankmates - I left him in the main tank until the end as that seemed best for him; a few others were less sociable and I moved them into an isolation tank where one did much better as it wasn't struggling so much with the filter's outflow, one didn't get any worse, and one was actually best moved back into the main tank as the stress was clearly going to outweigh any benefit. Eg 2: my first cardinal tetra responded badly and in a stressed way to medication and treatment; I was therefore reluctant to move and medicate the next; the third absolutely refused to be caught to undergo treatment despite best efforts, and its shoal-mates were very protective during capture attemtps.]
Thank you for your response, it was thorough and informative! We treated the tank with salts and the Danio has improved bloating. We are also doing fresh feeding of whole tank for few days as well. He's still very active and happy in the tank so we will wait and see how he progresses.