Can't match problem to any description I've found ANYWHERE

I have four plants that are exactly one month old today. A couple days ago I noticed a dark spot at the very tip of the lowest set of leaves on each plant. The spot has grown slightly on each plant, and on a couple of the plants these lower leaves have started to yellow from the inside out. The veins of the affected plants are very red/purple. On one plant the leaves did not yellow, but several more blotchy spots have appeared on the same leaf, closer to the base. The plants have been on a 12/12 light regime since germination. Right now they are under four 26 watt daylight cfls and sit in plastic cups. The plan is to move them under a 10 bulb cfl light fixture I have right after the plants I have now finish budding. I have used vegetative nutes on these plants a couple of times to promote minor vegetative growth early on before the flowering began, I am planning on feeding Jack's Bloom Booster next but am waiting incase I have some kind of nute build up. I will post pictures soon. Can anyone diagnose this from my description.

12/12 from seed under 104 watts under a blue light spectrum? You're missing the red light sectrum.

A plant that is 4 weeks old should not be in a plastic cup for one. It's okay to germinate seeds and keep a small seedling in a cup, but once the roots have taken hold, it's time to re-pot. Your plastic cup probably doesn't have sufficient drainage and aeration, so the young roots may suffocate. Also, go easy on any nutrients you feed your young plants. Most soils contain enough nutrients to sustain a plant for two weeks or more.

Yeah I know low wattage and I know no red spectrum. My ten bulb fixture is 7 2600k bulbs and 3 6500k bulbs. I just don't have the space under it right now. Also, I'm switching to two liters, I just haven't had the time in the last couple weeks that I was hoping I'd have. I've had family visiting the whole time for the holidays. Anyways, I forgot to mention that I'm growing hempy style, perlite and vermiculite medium with a small hole in the bottom of the cup. I think drainage and aeration has been okay.

.....i.agree witb all you guys....and georgeyboy you described the problem then drifted off from findingvthe soultion.....youve got yellowing leaves starting from the inside out...its sounds like you have a mixture of a zinc and calcium deffenciey check the forum and be youre own judge tjo ...thats what id do... Itz in the marjana problems section... Itz called a guide to nutrient deffenciey toxicity....good luck

I looked at several guides before making this post. I also reread the plant problem and nutrient section in Jorge Cervantes bible, which i'm not a huge fan of by the way. Ed rosenthal seems much more informed. Anyway I couldn't fInd a definitive match so I Posted my own thread. I'm uploading pics now. One plant looks different than the others and far more severely affected. If it is calcium, will adding some eggshells to my perlite vermiculite mix before transplanting solve the problem. Thank you to everyone for help and input.

What your runoff ph looking like? I had a Moby Dick on the 5th week of flower that started showin interveinal yellowing and looked blotchy, mainly lower leaf nodes. According to the manufacturers strain review it was suseptable to locking out iron with slightly acidic ph. Sure enough I checked the R/O and it was a little over 7. I flushed with ph adjusted water and knocked the problem out in a couple days. They've recovered fully.

I never check the ph of the runoff. Just adjust ph before watering. I'll make sure to check it after my next watering though thanks. I couldn't upload pics from my ipod at work, so I'm waiting for the lights to come back on in a couple hours then im going to take pics with my digital and upload them. The most affected plant is also incredibly droopy. How bad will this affect my yield?

That sounds just like my problem, my leaves looked droopy too. You may give them an extra week of veg to let them recover but mine turned out fine.