Plants, time for

This goes best by variety, I think:
2 tomato varieties from seed. 4 starts - these are my backup in case I need to impress someone and everything else sucks. One is a cherry, which we don't really care for, and one is a determinate, which we really don't care for. The third is an Early Girl, which everyone apparently cares for. Then we get a Big Beef for $.32. Immediately the Early Girl, followed by the cherry and determinate, yellow and die from the bottom up. I realize that healthy sod is not an indicator of healthy soil, it might even indicate the opposite, but either way my soil is delicously nitrogen-free. I should have tilled the grass, worked in compost, blah blah expensive. I buy a 50-lb bag of 16-16-16 (recommended is 5-10-10). I spread the overkill in granular form around my plants, too little and they die, too much and they burn, and I have no idea how long it takes to work. So I throw a little food out when I go check on them everyday, even though the stuff from before is still there. It's exactly like caring for a dead hamster.