Found this but with only a few typical responses and no post of a resolution.
Typical response was cal mag or nitrogen deficiency
c/p (pics) Yellow veins?
One of my plants has bottom fan leaves are green
with VERY yellow veins. The leaves are slowly turning completely yellow. It's working it's way up. The new leaves are even worse. The buds don't seem to be stunted but they are yellow. There is no sign of burn/scortched margins or tips. I tried to do a search and only found the opposite "yellow leaves with green veins" So what does yellow veins mean? I thought it was a over fert problem and flushed it good but it only seemed to slow it down. I am thinking nitrogen deficiency but the new growth isn't stunted, just yellow.
Attached Thumbnails
End C/P
Most deficiencies are usually ph related. Like a ph higher than 6.5 for soil will lock out Iron and Manganese.
Late stage sulfur deficiency will be mostly yellow not just veins.
Only other thing i can think of it bugs sucking the juice out of it.