re: Tips for my raised garden

You didn't mention how deep you have your raised bed, only that it is 16x4. The depth of the mixture you have on top of your clay soil may not be sufficient to supply all the nutrients your plants will need.

My raised bed for root crops is 12x4x1 ft. deep and I tilled the clay based soil to 8 inches deep where the raised bed was going to be placed. Then I filled it with a good garden soil I got from a local soil/mulch supplier and turned it under to mix in some of the clay based soil.