Mic Cable Length Issues

I have a mic run from the board of about 100' to the stage left sub woofer. When i jump from my stage left sub to the stage right, about 100', I have trouble with the sub I'm jumping to. It doesn't have the same power as the home run. I have changed the order, same thing. How can I get from one sub to the other without losing signal?

When you say that its the same when you change the order, do you mean that its always the same sub, or always the second sub?
I've rarely had issues running 100', what cable are you running?

If you're driving a balanced signal over a balanced cable, you shouldn't be seeing any noticeable attenuation over that distance.

Are you indeed driving from a balanced output of your mixer? (Not an RCA aux output)
Have you verified with an ohmmeter you have continuity across all pins on each cable, with no shorts between pins and no flips in polarity?
How are you performing the wye? Are you using a wye cable with XLR's, or are you using a loop output built into the subwoofer?
Do either subwoofers have built-in gain knobs or DIP switches for assigning level or crossover points (80Hz, 100Hz, Bypass, etc.)?

Photos and make/model of both subs and the mixer would be helpful.

Have you tried moving the sub to a closer location (temporarily) and using a different cable (or an alternate 100' cable) to verify the cable does not have issues (as MN indicated above)?

I suspect an open connection on pin 2 or pin 3. On a balanced line, that would result in 6 dB of level reduction. Check the cables for continuity and you'll find a broken cable.

To put it in perspective, did a car show a few years back and ran over a mile of balanced line between the mix and several powered speaker units. Couldn't detect any drop-off between speakers.

It could also be a matter of the subs you are using and what controls they have on them. If you are using XLR to drive them, I’m assuming they are active subs. Some subs have volume control for the output linked to other controls, so you may want to check that.

Adding to what Mike said, are you sure that the XLR output on the sub is an unprocessed loop through and not a filtered output for a Mid range box or something?

Then there's always this
https://www.controlbooth.com/threads/mystery-low-monitor-level-with-answer.42218/