Cascade amplifiers with different corner frequency
What I have noticed is that the cutoff frequency is different for both
  cases, but I dont know why, since both separate circuits have the same
  cutoff frequency and gain.


They certainly don't have the same gain. The non-inverting stage has a gain of: -

$$1 + \dfrac{1400}{100} = 15$$

The inverting stage has a gain magnitude of: -

$$\dfrac{2000}{100} = 20$$

Based on this, they are bound to have different cut-off frequencies. Here's why (using a typical bode plot from an op-amp): -




At a gain of 20, the 3 dB point will be 430 kHz
At a gain of 15, the 3 dB point will be 630 kHz


OK it's a different op-amp to the LM324 but the principle is the same; the lower gain setup will have a cut-off frequency that is circa 63/43 higher than the higher gain setup.