Lynch Box Serial Loop Problem

Run down of what happened today:

-Bumped Line 6 M9 pedal into the corner of the amp where the power and standy buttons are. Made a loud pop. Lost half of my volume.
-Jiggled all cables on amp.
-When unplugging and plugging back in the 1/4's to the serial send/return, this retuned volume to normal, but made loud pop everytime I plugged into the loop.
-Played more, but popped again, and lowered the level.
-Changed fx loop preamp tube. Seems to have worked.
-Preamp tube, before change, barely lit. Tube near the input lit very well. PI preamp tube not as bright.

Should all the preamp tubes be somewhat the same brightness?
Should I think that my fx preamp tube was causing the pop and volume loss, or maybe a power switch is bad since that is where I bumped into the amp with the pedal? Thanks.

I don't know about the switches. The box my Lynch Box arrived via UPS looked like it had been dropped, and it was torn. Nothing wrong with the amp.

I'm allergic to electricity. does the amp pop and/or work fine without the M9 connected?

It did pop without the M9 connected. After the preamp tube change, it didn't pop. I played for about an hour after that. I will put more time into playing tomorrow and see what happens.

I'd guess the effects loop tube was on the edge of dying and that knock with the M9 gave it it's last blow

To awnser your question: not all preamp tubes glow the same, as they are different construction.
EHX's glow considerably less (or the glow is conceiled by the construction), I believe JJ's also have less visible glow than most tubes.

Are the tubes all the same brand and type?

If so then there's still a chance that it is just natural, since every tube is unique