What's up with this leaf?

I found a few leaves like this hiding on one of my plants. What's causing this? I'm growing white widows in soil and using 1/2 strength nutes. I'll be bringing them down in about 3 weeks.

It could be the 1/2 strength nutes. Looks kinda like a big 3 micronute deficiency Cal, Mag or Iron. And/or Ph lockout, which would cause a deficiency as the nutes aren't made available to the plant.

On the Oddball, strange and unlikely front..... Do you have a Hops Vine??, or Does your jackass nieghbor have one???, or worse... did you bring one into the grow room too do a little re-fuckulate grafting experiment???? IF so, and IF the Hops looks like that, but 10 times worse.... it might be Septora. A disease that is not uncommon for Hops to have, and spread to its Cousins..

Was it a leaf hidden down low, amongst the foliage, getting little light? If so, don't worry about it, sometimes they die off naturally, 'cause the plant no longer needs them. If it looks like a deficiency starting(spreading), then it's time to investigate further.

Thanks for responding, but no hops and the leaves were in the back of the plant getting plenty of light. All of my plants have been getting 1/2 nutes for the past week and only one of the plants has leaves like this.

looks like an old leaf dieing like they do

Septora is rare... but I like to ask. I am hyper-aware of Septora .... because I have 5 hops vines. 2 prime ladies, 1 unknown lady and a 2 unknown males. I either have severe P deficiency on some of the old growth on the Males.... or Septora. I am very conscious and aware of the potential cross-contamination problems, and very pro-active at handwashing and making sure I dont walk anything in.

But yeah, there is the occasional dying leaf thing which just means your 4-6 weeks into flowering.