That doesn't sound right. The way you can check (usually, though of course it's not classic) is to look on Lucy.
Malo (
stacking)
Malosi (
stacking)
Malosini (
stacking)
They list each other on their stacking pages, so in theory they shouldn't stack. Tash however is not listed, so it should (and I believe does) stack.
Someday I'd like to create a "sequel" to the
http://wiki.project1999.com/Buff_Lines page, but for negative effects. However, it took
a lot of time to make that page, so I don't plan on doing the sequel anytime soon.