If your LR
was cured you may not see a cycle because the rock has benificial bacteria on it. How long have they been in the tank??
If its been a few weeks then i would say that the LR
is cured and its doing its job and taking care of the ammonia, nitrites ect..
If you see any spike at all just leave them in till the cycle is over is there is any left take it out then.
I used cured LR
in my 55 and it never showed a cycle, so its possible if you have good LR
with no die off to have no cycle.