Odd Problem - Please Take A Look At Pics

I've looked at all the charts/pictures I could find and none of them seem to match what I'm seeing here.  Not even close.
 
I've got 5 plants (bagseed) outdoors in 5th week of veg.  All planted directly in the ground but with 5 gallons of new soil (potting soil, compost, organic steer manure mix).   The other 4 plants are doing fine, it's just this one.
 
This was my best plant until recently.  Now the growth has slowed and the new growth is unhealthy.  Most of the leaves on this plant look fine except what you see in the pictures.
 
Ignore the white dust stuff you see on some of the leaves.  That's a powder insecticide that I was sprinkling around the plant base when the wind picked up and blew some on the leaves.  Plant already looked like this prior to the insecticide.

 

Wattering is drip irrigation - 1/2 gallon every night.  Soil is well drained - moist but not wet/soggy.
 
So far this spring we've had a maximum outdoor temp of approx 82*F.  
 
Thanks

 

I've spent the last few hours looking at charts, etc and still don't have a clue as to what is going on here.
 
The closest I can find to a match is a potassium deficiency.  But from what I've read, this typically shows up on all leaves and mostly on older growth instead of newer growth.
 
My only other guess is some sort of a bacteria or virus
 
Hoping you guys have seen something similar or can offer some advice.

 

Mixed well in a wheelbarrow.
 
Potting soil was 3-3-3.  Organic compost and steer manure - who knows.
 
The other plants are doing great in the same soil and temps.   Not sure why only this plant would be suffering, but I supposed it's possible it got stronger nutes or something.   Hope it's not a temp thing tho as summer is just getting started and we'll likely hit nearly 100* on occasion.