The squash and cucumber produce separate male and female flowers. You can tell which is which because the female one has a tiny fruit behind the flower. They both have to be present at the same time and there have to be bees or something to move the pollen from male to female. Frequently early in the season the plant produces just male flowers first. The male flowers open for awhile and then die. The female flower does the same thing if not pollenated.
Blossom drop in tomatoes is a sign of stress in the plant. Plant goes into survival mode, drops the blossoms to concentrate on growing the plant instead of growing fruit. It can be any of a variety of kinds of stress:
temperatures too low or too high, humidity too low or too high, too much or too little nitrogen, lack of water or over watering. Early in the season blossom drop often relates to night time temps going below 55. It may be caused by the use of excess nitrogen fertilizers or dry windy conditions, but the most common cause is temperature extremes. If night time temps are above 75 or if the day temps are above 90, the pollen becomes tacky and non-viable. Pollination cannot occur. If the bloom isn't pollinated, the bloom dies and falls off.
So you have to figure out what is stressing your plants. If your high potassium fertilizer also has nitrogen with it, I would tend to agree with TZ that every 10 days is too often, especially if you are using it full strength.