Tubes and their problems

Microphonic tubes are usually ones that soon will blow.
You can tap amp chassis and if you hear tapping via speakers, your tube(s) are about to blow and you'll need to determine which ones by swapping between channels.
I would use sewing needle or similar that is able to go outside of contacting flaps and inside the socket and work on each one. Slight bending of tube terminals may also increase contact strength.
Tube that can't reach desirable bias may also be bad as well.

Clean the top surface of all tube sockets just in case. It is often arcing from one pin to another via dirty sockets that produces the pop or crackle.

I heard popping from my Jolida FX-10's tubes on my right speaker. To see if it was the tubes, I swapped all the tubes from left and right channel and visa versa. The popping then happened on the Left side.

This proved it was the tubes - I went ahead and replaced all of them, fixing the problem.

If you do the swapping as mentioned above, and the popping continues on the same channel, then it's Not the Tubes.

The idea that a microphonic tube is one that is going to blow is incorrect. Microphonics is a construction issue but not an indication of imminent failure.

@ Joeylawn, its likely that only one of the tubes you replaced was actually the one giving you troubles. To find it, swap the tubes left for right one at a time rather than the whole bunch.

Atmasphere, you're right, but I just went ahead and replaced all 6 tubes (which were Electro Harmonix and Tung Sol) with matched and cryo'd JJ's.