As a Canadian I don’t see Napa here . As a ford master tech . I have used a bit of oil absorbent . The most common products are DE and fullers earth .for bonsai I use DE fullers earth looks almost identical it is heavier enough dry to notice it picking up a bag . It is also a more consistent colour like the lightest colour of DE and all the fuller is the same colour . I quit bonsai for 10 years restarted 2 years ago . As winter just ended and trees un thawed . My suspicion was proved correct . I have 2 trees the absorbent has turned to mud .
I believe the culprit is Covid most likely supply inconsistency forced bags of DE to be filled with fuller earth . I don’t think there is bad batches of DE I never had a concern before . I recommend soak and freeze a sample as a test . Fuller turns to mud .