My spinach develops some slightly large swellings and in the end dries up. What may be the cause?
Effects of Alkalinity on Plants
Certified GKH Gardening Expert
I'm not sure the issue by just this description of 'large swellings', but my best guess would be some sort of insect damage.
The dried edges could be from the same issue, or possibly a watering issue.
Neem Oil is a good treatment as it acts as a fungicide and pesticide if you want to attempt to treat the spinach.
Spinach does prefer to grow in cooler conditions.
Here are a few links for you.