I think the canary in the coal mine thing is great with regards to worms.
In my previous grow I had put them into my 5 gal smart pots for flower with my faulty soil mix using those messed up buckwheat hulls that caused a cascade of issues.
The worms all fled. Gradually at first but eventually there were close to none left in the pots. I started with 15-20 per pot initially...
This time around (with my new soil mix in which I replaced the buckwheat hulls with classic perlite), I have about as many worms in my 1 gal pots for veg. And so far, 1 week in, not one has tried to escape the pots.
This is even more impressive (to me anyway), considering that I way overdid it on cutting my soil mix further with perlite for the veglings. I think in some of the pots I have the soil mix which consists of roughly 1/3rd of perlite, further cut 50-50 (soilmix-perlite).
I did that because the soil looked very composted/compacted after composting in bins for over a month before planting. Felt too dense/compact/heavy so I stretched it further with perlite.
So far the plants don't mind and I expect they wont, it will just mean I need to put them into richer soil in 5 gal pots sooner than had I not further cut it with more perlite (or so I assume/believe/hope
Anyway, long story short, in some of those 1 gal containers, there is close to 50% perlite and 50% soil mix (with 1/3rd perlite). And the worms still don't seem to mind.
I was fully prepared for some of them to bite the dust but so far, I haven't found a single dead worm on the tarp below the pots.
Combined with how fast they multiply and happy they look in the soil bins, I take their behavior and multiplication as a sign of my soil being healthy - and so are the plants.