Your on the right path.
Testing your soil will help. Most soils have a severe lack of organic matter(decomposed leaves, compost, etc.)
That might be part of it. When I built the raised beds I ordered a truckload of topsoil. I was real disappointed with what was dumped. It was real heavy, lots of clay in it. So I filled the raised boxes with a mix of:
* 1 part Peat Moss
* 1 part sand
* 2 parts topsoil
The raised beds are 4' x 4' x 1' high. (16 cubic feet) I built them in 1997.
Last year's fiasco
Last year I added a coffee can of vegetable fertilizer in each box because I guessed that after 14 years the soil probably needed it.
Color me surprised. those 4x4 boxes can be seen from space. This google earth pic shows them behind the garage.