Yellow/greenish pattern on 1 leaf?

So here is a pic. The plant is very healthy but has this one leaf that is exhibiting these markings. Anyone know what it is and how I can fix it?

edit: I should note its about 17 days old and I've only fed it nutes (at 1/4 strength) once, 3 days ago, and it had the marks before that time.
Soil is FFOF.


Thanks

bump

I checked the sticky, but I can't seem to pinpoint what is going on. I've used nothing but distilled water and FFOF soil, with 1/4 strength nutrients right when they were 2weeks. The markings were occurring before the nutes were first fed. Could it just be the FFOF is a little too strong for that particular plant? Maybe there is a "hotspot" I read about where the soil was slightly unevenly distributed leading too many of the pre-ferts to affect that leaf. I'm just theorizing here.

The plant as a whole looks a-okay and no other signs of illness. The one other plant I have has slightly more of a brighter shade of green but I don't know if that is necessarily unhealthy because this is all bagseed.

Thanks for your replies

bump again.

doesn't seem to be spreading. plant looks healthy. they are in darkness right now.. can check again in a few hours.

helps appreciated

Slight def. Maybe N. Give it a bit longer then increase nutes.