Beans and broccoli don't like cold feet. What are the overnight temps in the garage? If below 50, you might need to use a low-temp heating pad to keep the soil warmer; or move them indoors near a sunny window.
They also need many hours of light. You might also try leaving the lights on in the garage 24/7 so they get a lot more light.
Beans cannot tolerate any frost, so plant after all danger of frost, waiting until the soil is somewhat warm. When beans emerge, thin to 6 inches apart.
Sow your Broccoli and Cauliflower seeds at a depth of 4 times the size of the seed, or ½ inch deep, and water thoroughly. Once the seeds have sprouted, be sure to keep the soil lightly moist.
Make sure the plants receive plenty of light " fluorescent light for around 14 to 16 hours a day is also ideal for the fastest growth. You will want to keep the seedlings just a few inches below the light so they don't "stretch" and get "leggy". If you don't have fluorescent lighting, a south-facing window will do just fine.
Transplant your Broccoli and Cauliflower seedlings when they have at least two sets of true leaves. This should be done about 2 weeks before the last frost. Site them in full sun in a rich, moist, well-drained soil, spacing the young plants 18 to 24 inches apart in rows that are 2 ½ to 3 feet apart. Feed both your Broccoli and Cauliflower with a low nitrogen fertilizer when first planting out. For your Broccoli, fertilize again when the plants are 6 to 8 inches tall, 12 to 15 inches tall, and then when the buds first form. For your Cauliflower, fertilize again every 4 weeks. Keep the seedlings well watered and mulched to retain moisture and keep the roots cool.
If your seedlings have been held too long or mistreated in some way before planting, they can create "buttons", or small heads, that tend to flower prematurely.
Climatic elements such as extreme cold and drought can cause your plants to halt their full growth and form only "buttons."