Till your vegetable patch water it everyday, let the weeds come up. When they have at least 3 leaves pull it. Make sure you get the roots of cut and come again weeds. Repeat tilling watering,weeding, until you don't see many weeds coming up. Do a soil test if you have not done one. Add your amendments 4-6 inches of a blended compost, 1/2 inch of manure on the garden bed . Add the recommended fertilizer and adjust pH if necessary.
Spotty plants will provide more light and soil for weeds to germinate. Try wide row or French intensive gardening which does not leave much open space for weeds to grow.
If your seeds are good, then the soil prep needs to be better. Water consistently with a sprinkler or drip system on a timer. Seeds need even moisture or they will die.
Since you live in Wisconsin, some of your plants can be started indoors prior to setting out. Grow a few extra to fill in for the ones that fail. you can start all your plants indoors and harden them off to plant outside or plant a few extra pots at the same time you plant outside so you can fill in the blanks with your extra plants that will still be the same age. Corn, plant every 8 inches instead of every foot. Plant in a block. If it is too crowded you can take some plants out.
When you buy seeds make sure they were in the temperature controlled store and not outside exposed to the sun, moisture in the garden, or temperature fluctuations. Keep the seeds in a ziploc bag in the refrigerator until you need them. Put the seeds in a bowl of warm water over night, toss out the floaters. Plant the rest. Make sure you put a barrier over the seed bed. Birds and rodents will come around and dig up the seeds to eat them.
Corn and beans will do better after the weather warms up a bit. Peas can be started earlier. Pay attention to your local planting dates. You can look it up on the Farmer's Almanac. For corn and beans they will do better once the temperatures are consistently warm for your varieties and the days lengthen. Where I live I plant most warm season crops on Mar 1. Before that they dampen off more and the ones that do germinate grow very slowly. Peas can handle cooler weather. I also grow tropical corn and flat beans because they don't require long days, but they like it in the 70-85 degree range.
Corn is a heavy feeder and usually needs side dressing of nitrogen. Beans can follow the corn since it does not need to have additional nitrogen. I follow my corn with Asian vegetables and cabbages since they will scavenge any excess fertilizer. I rotate my beans with tomatoes in pots. It is where I have a permanent trellis for cucumbers, tomatoes, beans, and peas.
Happy gardening in Hawaii. Gardens are where people grow.