I personally don't see any reason why not to. People talk about them needing different things but other than food I am unsure what they mean by this and even food is not really a major issue.
If you have coldwater fish that do not require really cool weater and tropical fish at the lower end of tropical, then I thik it should be ok.
I had my tropical tank at 75F at one point because there was coldwater loaches in it. My coldwater tank at the same time was at 73F, so 2F is not much difference to them and 75F is fine for many tropical fish.
However, the question is why? Is it out of necessity? I wouldn't advise buying coldwater fish for a tropical tank but IMO/IME experience it can work. I am unsure of the long-term effects of this as I have read about motabilism increasing thus leading to a shorter life span, but I am sceptical whether this would occur due to a 2F increase.
HTH