I use Yosemite with Chrome version 42.0.2311.135 (64-bit). When writing in a text area the spell checker correctly detects English and French, but does not detect Spanish, and so it marks as wrong correctly written Spanish words:
I don't know why it happens. English, French and Spanish are set in Chrome:
and also in the Mac preferences:
Is there any setting to have Chrome/MacOS detect Spanish like it does for French and English?