Have you noticed the same symptoms on other garden plants? Do you know if curly top virus is in your location? This virus is quite broad spectrum in its host plants...the vector is one of the leaf hoppers. That's just a thought, however.

I agree, it does look like aphid damage.

I researched curly top virus (CTV) and the sysmptoms of my plants don't match the symtoms of CTV. In a case of CTV leaves curl upward but my plants are curling under. My plants have none of the other symptoms. If anyone is interested in reading about CTV here is the website I used. It's owned by New Mexico State University.

http://cahe.nmsu.edu/pubs/_h/h-106.html

After checking my whole garden it looks like my spinach is the only crop aflicted. My spinach has also gone to seed in the last two or three days so I don't know if it related. None of the leaves have any spots, bumps, powder, slime, etc . on them.

Maybe I'm just missing the aphids? Ninja aphids?

Thanks for the suggestion. Anyone else have an idea?

Check deep inside the folds of the spinach to see if aphids or mites have done the damage.