My spinach came up nicely, but all the plants have tuned yellow and are wilting. What’s happening?
This could be due to too much or not enough water and/or fertilizer. Vegetables need water to grow, but too much can make them soggy and cause rotting; the same with fertilizer. The best fertilizer is well rotted compost, which gives the plant all it needs without overdoing it and causing burning.
It might just be the weather. Spinach prefers cool – moderate temperatures. It is one of the crops you can plant early in the season and not worry about a cold night. When the plants get overheated, the leaves yellow in protest.
Next, it could be pests. Aphids love spinach and an infestation could cause the leaves to turn yellow. Aphids are quite visible – a good blast with the hose everyday will keep them at bay.
Now for the really bad possibilities. There is a fungal disease called Fusarium wilt, which causes spinach leaves to turn yellow. If this is the case, plants should be destroyed and next year, you should plant something different that is not affected by this disease. There is also a virus transmitted by cucumber beetles called Spinach blight.
See PEI. Spinach Pests and Pest Control (2003) https://www.gov.pe.ca/af/agweb/index.php3?number=70498
And, Harvest to table. Spinach growing problems: troubleshooting (2011)