4 white widow ~ femed.

[Greymowser]

Ok here's the poop. I am 13 days into flowering. I had some trouble in the veg stage with heat stress & nute burn. (I think) and I thought I had it under control. I watered yesterday with good ph balanced water and tested the ph down in the soil with a probe. It was a bit on the low side. (around 5.5 to 6.0) I did some pruning of the leaves that still looked sick. it's now getting close to lights out and when I last checked on them I found more yellowing/ blotching/ crispy tips. I'm sure I don't have the light to close. It's to late in the game to fail. any advice would be appreciated.
Tent ~ 4x4x7'
light ~ 600w hps.
Fan~ 9x9" floor.
Exhaust ~ see photo's
I use a cool mist humidifier due to low humidity.
I was using Fox Farm grow big (6-4-4) but I got gun shy so I have not fed them anything for 2 weeks.
Other than the nasty looking palm leave what do you think?

[NAKEDGARDENER]

To me the fan is blowing directly onto the plants, have you tried a two fan internally, one situated on tent pole in corner above the canopy but blowing the air over the canopy indirectly, then second small fan lower down to circulate air in clockwise or anti clockwise direction, seems spotty almost like mold but could be wrong

[D.A.A.S.69]

Morning Grey, What kind of soil are you using ? And them probes aint very accurate, unless you got one of them 100bucks one.
Brother that's a nice setup, you can't hardly beat a 600hps, I would love to try to help you, if i could, but I can't see sh-t ,in your pictures , can you get pictures with your light off ?
I'm sure some of these other people might have better eyes than me though, an Will be glad to help you.

[Cannabliss]

Something's definitely going on here, but It's a bit hard to diagnose the leaves due to the color of the MH lights. As you mentioned, there are signs of nute burn and/or light stress, so that could have been the cause and they're just recovering from it? How does the new growth look? Nice and green or still coming out all wack?