Strange discoloration is quickly taking over my plant. Please advise.

This is my first grow and I've been looking around for posts on something similar but can't find anything that looks like this. The plant is on an 18/6 light cycle and is about a month old. It's in Foxfarm Ocean Forest soil and I just started feeding it some all-purpose fertilizer last week at 1/4 strength.

The discoloration appeared during the dark cycle, and seems to be getting worse very fast. The plant is considerably wilted compared to normal too, and the tips are curling up and shriveling on the affected leaves. Yesterday I noticed some spider mites on the leaves and had been spraying the leaves with a diluted dishwashing soap solution every 1-2 hours to get rid of them. It seems like that might have something to do with it since the discoloration started appearing that night.

The first picture is at 6AM, the second is at 1PM, the third is at 4PM today. The last picture shows the discoloration on other areas of the plant.

Any advise would be appreciated. I thought things were going well until now, so I really hope someone can shed some light on what's happening here. I thought maybe it was nutrient burn, but the discoloration starts along the edges of the leaf, not necessarily the tips, and I really don't think I've fertilized it that much. Thanks.

Could have been the soap you where using. When I use a soap/water/bug kiiler mix I use dawn as that is about the mildest. I would suggest that heavy misting with just plain water and see if that helps. I'm kind of thinking residue left over from the soap clogging up the leaves ability to breath properly or even poisoning the plant. Killing spider mites with soap and water is a good idea, just rinse the leaves off afterwards with just plain water. Best done just befor lights out so as not to burn the leaves.

Diluted meaning what?
Couple drops per quart spray bottle is plenty.
You may be smothering the leaves, but it also could be a phosphorus def.
What is the formula of your nutes?
Any sudden drop in temps?
What is your PH?