I have had a repeated problem with my squash plants yellowing about 1/2 way through growth. For instance after the set some of the first fruit they go yellow. Last year I got good production even with the unhealthy look but it is still bothersome.
The hills are dug about 18 inches deep and back filled with mostly horse manure based compost and less of a richer compost made with household scraps, chicken manure, rabbit manure leaves etc. In the end there is about 1/2 compost and 1/2 garden soil. No scolding about soils test here.
My neighbor says the nutrients are leaching out and need to be replaced. I have read that compost doesn't leach like that? Other vegetable plants with the same regimen, or similar, all do great. Just the squash yellow. I am about to plant 1/3 acre of them and wonder if I should spend some money on additional fertilzer to make it through the season. I could compost tea feed them but at this scale that is not desirable.
I was thinking about putting 1&1/2 cups of Dr. earth per hill but don't like the expense of it.