Starter Plants from Seeds

[GrandGarden876]

I am an accomplished gardener but have always bought my plants, ready to plant, from my local nursery. This year, however, I decided to start my own plants in a make-shift greenhouse out on my enclosed back porch. I bought seeds from a well known garden center and followed the directions to the letter. However, it seems my seeds did not do well and my plants did not grow as strong and healthy as those I had bought in the years before. Is there some trick to starting your own plants from seeds or might I have gotten a bad batch of seeds? I’ve heard that old seeds will not produce as strong of a plant as fresh seeds and I wonder if that has something to do with my problem. The packages didn’t have a date on them, which I found odd, but assumed they would be fresh because it was the first week they had begun putting out garden supplies. I did go ahead and plant my starters but I also bought a few already started plants to go along with them. Looking at them side by side, I can see how my starter plants are much smaller and weaker than the ones I bought at the nursery. How old is too old when buying seeds?