MY SATIVA STRAIN IS DROOPY AND MY INDICA STRAINS ARE THRIVING EVERYTHING IS THE SAME . LIGHT ,SOIL , NUTES, TEMP, EVERYTHING. WHAT GIVES?
If they're all being watered equally, let the sativa strain dry out a little more than the others. Droopy usually starts with either over or under watering. Over watering prohibits oxygen from getting to the root system, and roots LOVE oxygen. (I'm not saying you're over watering, it may be that your soil mix is moisture retentive also) Hopefully, this info helps.