I must design a 4-bit shift register circuit. I am pretty sure that I need 4 D flip-flops sharing the same clock. right??

So I did that and here is the result:
[![wat][1]][1]


  [1]: https://i.sstatic.net/Uu1YB.jpg


As you the LED lights are neither completely off (0) nor completely on (1) rather they seem to be in this, uh, indifferent state? Anyway, the point is, it is not working no matter where i put the switch.

If I go to each ff and remove the preset/clear lines the circuit works! but I do not understand why that is an issue? Why doesn't it just work the way I drew it?