I have never seen it turn white myself. I have heard that white could be MSM, but from my own experience this tends to lead to a white powdery non-crystal residue in the pipe stem, but not the meth itself turning white. That sounds odd.
If it stays liquified for 30 seconds that's extremely weird. Might not even be meth. If it was a cutting agent, that is NOT a normal cut and could be dangerous.
Your low or middleman dealer probably cut it with something stupid or unusual, but again, it could be anything, and not something we can accurately ID for you here based on description.
This question does borderline on topics we cannot cover here, since we cannot ID drugs here, and that sort of includes what drugs are cut with. The only way to really know is to send it to a lab, such as drugsdata.org, and have it tested by GC/MS.