There really isn't enough info here for me to really be helpful.* Any idea what was in the "garden bed mix" from the nursery?* Was it a brand name bagged product?* Was it organic garden soil or did it have a slow release fertilizer added?* Was it peat moss based?* Just not enough here to know what you used.
When you say you planted "all the regular stuff", I really have no clue what that would be.* If you planted tomatoes, cucumbers and squash, they would all be in the same family and the problem could be related to their needs.* But if you planted green beans, potatoes and corn, none of those are related and the cause of the problem could be different.*
overfertilizing which can cause plants not to be able to take up needed nutrients or can cause rootburn.
soil missing essential nutrients
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.