I have not heard very marked differences between interconnects simply based on a half metre difference in length except where there are electrical interface issues or where the noise level picked up by the interconnects is significant. It could be that the length itself caused the change, but there are other possibilities to think about.
Just thinking aloud, I can think of a few possibilities....
Perhaps you had forgotten how good your system sounds while they were away. I kind of doubt this one.
Perhaps the 1 metre cables developed some oxidization around the joints to the connectors. You have freshened up one end and got an improvement, which could mean the other end might be similarly improved if they were reterminated. I doubt this one as few high end interconnects are so badly terminated that this happens much these days.
The other possibility is the cables pick up noise either because of your RF/EMI environment, of through the cable making contact with magnetic or vibration prone objects, or something similar. The half meter cable will be less prone. I tend to use the shortest possible interconnect I can get away with simply because it becomes easier to 'dress' the cable so that it does not touch anything but air and stays away from other cables. This is always harder with 'over-length' cables. This is the one I would guess could be right. the 'over-length' 1 metre cable would have gone on some kind of journey that the half metre ones do not. Sometimes proximity of one cable to another can have enormous effects - cable dressing really requires a lot of experimentation and listening that few of us have the patience or desire to do every time we change something.
The other possibility is that there is some kind of impedence/capacitance issue such as the cable has highish capacitance or the cables are not a great match for the task of linking your source and destination components, or the impedence match between source and destination is just a poor match. All of these are just different ways of saying the same thing. If any/all of these are true, then by halving the capacitance of the cables through halving their length, you are improving the electrical performance of the interface significantly. But this suggests there really is a fairly severe problem with the component match or the suitability of your cables for the task. Given you know what you are doing in this hobby Mejames, I doubt you would have selected this combination of components if this was the problem.