Simple problem, pics, don't want to toast another crop

See pictures. I think I misdiagnosed this last time it happened, asking for help this time. This will be the 3rd crop in this setup, first was a raging success. The only concrete change is that I used CO2 on the first and tried SCROG on second (they seemed to burn, I think they weren't moving enough.

Facts;
Nirvana Big Bud, germed around 5 wks ago. Raised under 6-42w CFLs in small pots until a week ago when I noticed them stalling. Transplanted to 3gal soil mix (Roots Organic, pretty free draining) and started them under 400w HPS. Temps 70-80s, 24 hrs on. Gave one dose fert (fish shit) about the time I transplanted. I had been watering daily while they were in the small pots, cutting back now but soil still a little heavy. Haven't watered in 24 hrs now, except for two which I flushed last night (no visible difference after 18hrs). I also raised the 400HPS and reinstalled the CFLs down low so they would get light without cooking. My pH and soil tester kits never seemed to give good results, so I haven't tried it again.

Stems are strong, new growth looks good, just the older leaves look wilted and feel dry. Some brown spotting. 3 finger leaves yellowing. New growth lighter green than old growth.

I want to flip them to 12/12, but not if they are ready to crash.

Just flush and hope for the best? Get a decent pH/soil tester? Pot too big, too much energy going into root development?

Please help. This is really frustrating and kinda scary since the last crash is going lead me to being short if these don't flower soon!

Thanks,
Banzai

let em totaly dry out, atleast for 1-3 more days, and move your light about 8 inches from the tops, and the other thing is use a hps for flowering, not for veg, mh for veg, (for next time) and when bud'n , just loose the cfl's ther a different spectrum then hps, it will just cause more veg down low. they look perty good though, just let em dry and then start feeding again, hope this helps

Plants be planted at least three feet apart, stacking them too close will result in stunted plants. The plants like some water during their growing season, BUT not too much. This is especially true around the roots, as too much water will rot the root system.

A marijuana plant that gets a lot of light during the early stages of growth (in the spring and early summer) will start to flower when the number of hours of sunlight decreases in the late summer and fall. So lighting schedules are important as well as the quality of light.

I would invest in a nutrient tester; your EC should be around 1.7-1.9; ph should be maintained at 5.5-5.9. Water your babies every 3-days or as needed could be sooner or later. Soil should be a little dry before you water them. Don't water your plants simply because you're on a routine; make sure your plants need water.

How many watts are you pushing with those lights? You need at least 400 watts during the veg stage and should upgrade to 600 watts to support your lighting needs.

Hope that helps.