Is your floor a 5-piece deal? Three sections in back, locked together with stringers, then 2 sections in front that are not locked to the others? (possibly some variation thereof - 2 sections in back, for example.)
Having a bit of flex between the main and front sections is normal (the operative phrase, which, of course, is up to interpretation, is "a bit". It will flex, but the boat shouldn't fold up on you, either.) There shouldn't be a great deal of flex within the main section of flooring.
If the floor pieces have come apart while running, something is not right. I'd suspect (as others have said) pressure in the tubes, or lack of stringers (the side pieces that lock the main floor pieces into a single unit.)
If it came apart between the front section and the main flooring section, I'd suspect pressure, most likely in the keel.