Bandpass Filter Balanced Ports

With the photos, I'd venture that you have stray capacitances all over your circuit because it is on a solderless breadboard. You shouldn't be doing high frequency work like this on one of those. Of course, this doesn't rule out parasitic effects addressed in the comments to your question, but there is a gorilla in the room, and it's the breadboard.

Your low pass filter is loading your high pass filter. Think of a simple voltage divider: . In general, if you have 2 circuits connected together, the first one's output to the second one's input, you do not want the second one to attenuate the signal that passes through the first one. Therefore, you must make sure that the second circuit's input impedance (represented by R2 in the voltage divider) is larger than your first circuit's output impedance. How much larger? The rule of thumb is 10x larger.

The output impedance of your high pass is roughly the value of R1, or 10 kOhm. The input impedance of your second circuit is also roughly R2 = 10 kOhm. So you need to decrease R1 by a factor of 10 or increase R2 by a factor of 10 (or some other combination such that R2 = 10R1) and adjust C1 and C2 accordingly to obtain the same cutoff frequencies. Once you do, you will see that your bandpass filter behaves much better.

Along the same lines, you don't want to increase R2 beyond 500 kOhm because your load is 5 MOhm. The same rule applies!