Pennsylvania,
United States 
I plant a small garden every year in the same spot. I have done this for about 6 years. I usually plant 6 tomatoe plants, 4 cucumber plants, and 2 zucchini plants. Last year my cucumbers and zucchini turned orange. I tried to eat one of the cucumbers, but it was sour. All of the previous years, they were normal. Does anyone know what would cause this? Is it a magnesium deficiency? Any answers would be greatly appreciated!
20 Feb, 2010
Answers
I agree Drc, soil born diseases can last for several years. Try growing your fruit in growbags or containers for at least two years.
Good luck with it guest. Oh I've just noticed you are from over the "pond" so might not have heard of growbags. These are plastic sacks of soil based compost with a balanced amount of nutrients in which you can grow almost anything. They are cheap, easy to handle and more importantly in your case will keep your plants away from your (possibly) diseased soil.
20 Feb, 2010
Previous question
Sounds as if you have exhausted/overused this small plot? may well have diseases too.
1.Chose another site which is probably your best option?
2.Give it a rest for a year and add well rotted manure.
3. Replace the soil with new nutrient/soil basedcompost etc but if diseases are present may not solve all your problems
20 Feb, 2010