I think you could be right, I've been using 3's on a 4C but have gone recently to 2's on a 5C. It seemed fine for ages but now, in the last two weeks I cant find a Mouthpiece / reed combination that I'm happy with for more than an hour or so.What do you use and how experienced are you? Maybe you need a slightly harder reed. I find the softer reeds go off very quickly and I now use 3s.
I find the Rico Oranges have a lot of variation - this is one reason they're so cheap compared to the 'posher' brands.About four months ago I bought a box of 25 Rico orange tenor reeds. I assume that they are from the same production batch, but I found that they seem to show some variation. So far all of them have played, but some seem to require much more effort than others. Among the solutions I use are filing the tip down ever so slightly with an emery board or soaking them longer.