I thought fasi is the plural of fase which is fem. except in plural it drops the e for i, but quale would remain fem plural?
Quale is never fem. plural. It's masc. or fem singular. The masc or fem plural is quali.
Despite the -i, they're all feminine plural :) Most words ending in -e in the singular end in -i in the plural, and they're gender invariant, so it's "la quale fase", "le quali fasi".
thank you to both for your help.