What's the issue? Yellow Leaves

Hi Folks,

I'm growing 5th generation clones of Gelato and had a new issue pop in generation 4. Through trial and error I think I have fixed the issue. I will put my solution at the end of this post.

I have been growing in both plain potting soil with my usual nutrients and in FFoF with just PHd water and adding CalMag in Veg. I got the same problem in every plant at week 5 of flower, what do you think?

She is at week 8 day 2 and I usually harvest mid week 10.

The damaged has stopped spreading and new growth seems fine and the buds are looking better than ever.

First I thought it was a lock out and flushed, then not enough nutrients, then too much. I was able to stagger through to the end with those test plants and got between 2-3 oz from each run but it was less than stellar.

This girl was grown in FFoF soil with only PH'd water and CalMag right up into week two of flower, then I started adding FloraNova Bloom. Then right on que at week 5 the problem showed up. So I figured it could not be a lock out since I used FFoF and water and I was feeding less than 1000ppm of nutrients for just the last 3 weeks so it was not nute burn.

The missing ingredient? CalMag! I noted it kind of looked like a problem I had with a Sativa in Veg one time when I was not using CalMag so I starting adding 4ml to every Gallon and the problem stopped progressing and new growth is looking real good.

I have never had to use CalMag in Bloom before on any plant and I did not need to for the first 3 generations of the Gelato nor do I use it on my 6th generation Kush clones in bloom. Genetic drift?

Thoughts? Suggestions?