2 week turmoil

I don't actually know if this is a fault, or if it's a feature.
I've built up my elemental and chaos resistances, but I keep getting hit with something that strips away my chaos resistance and lowers my elemental resistances, this continues on into other levels.
I've tried swapping out equipment etc, sometimes I can get it all back again, but it's very hit or miss.
I've tried looking elsewhere on the forum, but can't seem to find anything relevant