HPS all the way is FINE, and doesn't make node spacing that drastically different than MH, a little bit different, but marginally. I know many growers who use them all the way, just like some old school guys and certain sativas like to use MH all the way.
The stretch is from switching them to a 12/12 photo period more than from blue to red light.
I agree with overwatering, let them dry out! Sativas are very drought resistant, in fact many of them thrive when planted in larger containers and given a proper wet/dry cycle.
SOIL=wet/dry cycle
They should perk up once the soil dries out and they get to breath a little. Once they perk up I wouldn't water them until they tell you they need it. First sign that they start droping give them water. However long that took, subtract 6-12 hours and that should be how often you water.