Help ... yellowing fan leaves

My plants are about 3-4 weeks into budding when suddenly on two plants the bottom third of the fan leaves starting turning yellow and falling off.

Nitrogen deficiency? Or too much of something?

Want to hear what others think versus what I've read online. Any suggestions appreciated.

Am watering every 2-3 days and fertilizing once or twice a week (soil, not hydro) with Dyna-Bloom mixed with Liquid Karma

PS I picked off several of the brightest yellow leaves, like the one in the scan, before I took that shot ... sorry ... there were 5 or 6 of them like that.

When a plant goes into its 'hibernation' mode for the winter, it soaks up all the energy in its leaves and stores them in the fruit or the roots etc. Thats why in the winter all the leaves turn brown and fall off trees. Having a few leaves change color is okay in this stage of growth. The plants look very healthy and you should come out okay in the end. Goodluck!