Chlorosis?
 

I successfully grew spinach in my garden for several months. But then
most of them started turning yellow, some sooner than others.
Eventually some died and most of the rest were going to die. Then I got
rid of them and planted green bean seeds. The seedlings came up pale
green with some yellowing. As they grew they stayed very pale green.
Then I added some manure and they darkened a little but they're still
rather pale (although they are growing pretty fast anyway). I read
about chlorosis and I think that's what this is. I have some iron
sulfate and sulfur. Do you guys think I should use just iron sulfate or
both iron sulfate and sulfur? One web site recommends using both in a
1:1 ratio for trees. Another web site said that if you use only iron
sulfate, it rapidly becomes bio-unavailable to the plants in an
alkaline soil.