Yellow Spots, Crispy Leaves, Brown Patches.. What's going on?

Hi Folks

Need some advice please..

This is my second grow. 1st was Lowryder 2.
This time around I've got a few Big Bud Super Skunk in soil under 1000w HPS.
About 3 weeks from seed. Feeding every other water with the foxfarm schedule. Usually about 1/4 of the recommended dose.
Lights are on a 20/4 schedule
Temps are approx 75 lights off and 85 lights on
Humidity between 35 and 45

1 of my girls, at about 10 days from seed, had small yellow spots on the 2nd set of true leaves. I left it hoping it would correct itself! It didn't! So now at 3 weeks those yellow spots have developed into yellow/brown patches. Also the leaves are very crispy. Also it has spread up and through the plant

Please see attached pics

Any ideas as to the problem?
Cheers

Notice that most of the trouble areas are at or near the bottom of the plant. That suggests to me that perhaps you are
inadvertedly spilling some nute water on the fan leaves. When using nutes dissolved in water you have to make sure not
to splash the greenery. If necessary use a funnel to make sure you don't spray the whole area. I realize some nutes are
marketed to be used as a foliar spray, dissolved in water and sprayed directly on the leaves. But those tend to be greatly diluted.
Hope that helps.

BigSteve.

Ah, I've recently taken to light spraying/misting the inside of the tent to get the humidity up a little. In the process quite a bit of water got on the girls each time. Could this be the reason for the spots etc?

Is this then a form of mold?

Cheers BigSteve
Much appreciated