[drew51]

Beans don't like to be transplanted they should be sown in their permanent home. Best not to sow them in cups, but in the soil they shall live in. Yes use amendments, even though beans don't require much they require bacteria, and the compost, just about any compost will have them. Black Gold is a decent product. Some use inoculants, sounds like that might be ok too in your situation, Where I live the bacteria needed, appears to be in the soil. I constantly amend my soil. Compost for sure, leaves as mulch, maybe grass, coffee grounds throughout the year, straw, alfalfa meal, cottonseed meal, whatever is handy. Organic fertilizer at least a couple times a year. Onions are nitrogen hogs, you need to feed them well.