Both have some very small arrows I have failed to notice previously, although assuming the arrow points away from the source means amp 2 was wire properly but still made noise.
No idea how an RCA can be balanced for no balanced use, but there we are.
Generally found the cheaper cables to bee hit and miss as to quality and soldering hence buying these, no issues untill now.
Please forgive the blunt question ... but did your setup ever work right... or have you been having this problem all along?
One explanation could be a DC output on the amp's "sub out" jacks.
Another could be bad caps on the sub-woofer inputs.
Still another could be some kind of local interference getting into the amps.
There's a million variables here ...
I would start by pulling the whole thing down. Testing each RCA cable and checking voltages on all outputs and inputs. Then I would start building it back up one piece at a time starting with your speakers, then one sub then the other, then the amps, then your sources. At some point in the process adding a new device will start the problem going... and there's your bad actor.