Something's wrong with this picture.....Anyone know what it is?

So here's the lowdown...

400w HPS
PH around 5.8
Humidity around 60%
Adequate ventilation

Just did my weekly water change and they started doing this. Drooping a little and getting tan-ish areas on the leaves. When I did my water change I also noticed a large amount of bubbles, like foam, in my reservoir. Can anyone help?
I decided to flush so I'm doing that right now.

Looks a bit like nutrient burn. Maybe the excess bubbles are from anaerobic bacteria. Try some hygrozyme, flora shield, and a good res cleaning, pumps and all.

I've been following the chart for feedings, even doing it a little light just in case. I did flush my entire system, scrubbed res and ran clean water through pump/hoses last night for about half hour, drained, cleaned again and refilled with fresh nutes. I was thinking it looked a little like Mag deficiency?

Ended up being root rot. Added H2O2 every day, about 10-16 oz for my 15g res and it cleared right up. It was pretty bad root rot, thought my crop was done for but it's almost all gone now and plants look very healthy again.

Is the light too close, is that bleaching maybe?

No the light is about 8 inches away and it has a fan cooling it. left my hand right at the top of the plant to see how warm it was and it's ok.