Responses
I think it's implied enough that Abel and the physician did something to Hardy to turn him into an omega, and the only thing the physician gave him was that red tonic. That and the confirmation that turning someone into an omega by mere dominant pheromones of an alpha is pretty much unheard of... according to Shun.
Since Hardy brought up the fact that he isn't an omega as the reason why he wanted a divorce from Abel, and considering how possessive he is, it makes a lot of sense he turned Hardy into an omega. He also says how he won't have any excuses to leave him now after finding out about it... so... yeah...
I could be very wrong but based off Gray’s reaction to Hardy describing the medicine, I feel like Abel was actually giving him the illegal drugs that were mentioned that can change their second gender by force…. I’m really hoping that’s not the case. Abel and Hardy seem like a good pair cause Hardy always wanted someone who chose him and would do anything to be with him, and Abel wanted someone who would choose to stay.. I hope it doesn’t get to a point where he forces that decision ;-; I’m scared guyssssss