I personally prefer to change out casino issued with - thumb notch "Direct Fits". ---They're too loose upon closing.
I use the "no notch" Airtite brand direct fits which have no "soft foam" coming in contact
with what ever I'm storing- Coins , Strikes, Chips. It's my belief that any soft foam "black or white" in contact to the item stored-- will and does increase the surface area that can transmit moisture like a wick!!! The precipitate can be caused by invisible moisture/ Humidity "however low" it seems to be in the air at the time of encapsulation or periodic opening of the case & temperature fluctuations... to date "None" of my silver strikes that were transferred casino case to the "after market cases" have any "Bad additional tarnishing".
I do the strike or coin transfer case to case without any finger touching ( like separating a yolk from the egg white) type action/ manuver..
@ 10 to 15 percent were showing signs of mild oxidation, slight finger printing, and other anomaly's prior to my adding them to my collection, I try to avoid purchasing any items that show outward signs of mishandling or have been stored with foam rings..
A thing to consider is also the possibility that some of these chips may be "end of batch runs" or beginning runs and aren't mixed thoroughly, heated correctly, to much "dye ratio to plastic resin" when produced, and or Flat out chemical reactions to the storage material.
What a Rant***
Have a great day!!

Gabe Dobos LM 4143