The coffee stain was so light in the background that paint was added to begin forming the ground. The onion heads look washed out because of the amount of light hitting that area. The photo was taken under fluorescent and incandescent lights.
Paint to water ratio is so important and I know I've been using too much water in the mixture. The paint to consistency needs to range from tea, coffee, milk, cream, butter, with butter having the least amount of water and used very sparingly in a painting. Now to get this knowledge transferred to the painting.