my suggestion-Yeah it may be the case... I just thought it may take a little bit of time for him to adjust tocompletley different conditions.
regardless of stats when you get home do a nice waterchange and just wait. he is probably just sulking. bettas are prone to it. can take up to 2 weeks for them to come around.
just keep an eye out that no one is harassing anyone else in the tank. while ive never had a problem with it, some folks swear neons and bettas are a bad combo as the neons nip their fins (ive never had this happen tho). just something to keep in mind.
cheers!

But she really doesn't like my Odessa Barb 