Too much Nitrogen, or too little? Or is Sulfur the problem?

I have 3 plants growing indoors under a 400W HIS lamp. After a month under MH lamps for18 hours/day, I made the switch to 12/12 days under the HIS lamps 30 days ago.

There are nice buds growing on all three, with trichromes galore. I expect harvest will begin soon. Just one concern:

One of the plants has several yellow leaves. I tested the soil, and the readings showed the correct amount of P and K, but an EXCESS off Nitrogen. The typical results of having too much Nitrogen are very dark, not light, leaves.

The photos that appear closest to my problem I found here on this site indicating a sulfur deficiency. (In the photos I took, below, the color is off. The single leaf is more accurate, but it is still too green, the actual color is yellower.)

Any thoughts?

Also, is it too late to start with clones? Or must they be done during the vegetation stage?

You can take clones, but iv heard they're not as good, and its probably not good for your flowering plants, but as far as the nute problem sry i only have 2 grows under my belt

hi this sounds almost certainly like nitrogen lock out. you should flush and replace the top couple of inches soil, this should solve your problem within a couple of days. the plant is unable to take in the nitrogen due to a build up of salt deposits.

as for clones , i tried taking clones from a flowering plant out of six plants only two survived, one of which is still in limbo 1 inch tall 4 months old and deformed, the other very spindly, in my opinion not worth the effort.

all above advice is good, but also think about the plant. its flowering meaning coming to an end. During this time its dying off to produce the flowers it wants and that i know you damn sure want too lol!! plus your a month in already. if you want some more help this is where you can look to find your exact problem and diagnose yourself! =) https://www.rollitup.org/marijuana-plant-problems/216537-self-diagnose-your-plants.html well hope it helped happy growing and hope you get a BOMB yeild!! Smoke One!

Thanks guys, I'm giving Backdoor's advice a try. It's been 4 or 5 days and I THINK the leaves look less yellow. But I still suspect a sulphur problem, as another symptom that the plant clearly has is a purple stem near the top. I'm not too worried, since I'll be harvesting in about 2 weeks, and I don't believe at this late date it will cause much harm. Check out the photos . . .