Objects moving independently xcode

So, I have in my app 5 obsticles that move down the screen. I have a random number generator that picks a random number between 0-2 to choose the pattern that is going to be on the screen. And after they go bellow the screen they replace themselves on the top with an if statement that says if it goes bellow this point place it here. Here is the problem. At the start, it works just fine. Picks the number, matches the pattern. Great. But when they replace, they don't match a pattern, they just kind of go their own route. They keep about the same placement they get at the start, but then they move at small intervals around the screen. I don't know how it can do that because I have said that when it goes bellow the screen to place them at a specific point, not just choose its own random place. Anyone got any ideas on how to fix this? I do have auto layout off as well, and no were else in the code do I say to place them otherwise. Could it be that the starting code and the replace code are corrupting one another? I don't know. Anything helps.

Thanks! -Andy