Poor soil or overwatering?

I recently moved to a place with a yard so am trying gardening again for the first time in many years. I filled a large raised bed with cheap soil from Home Depot and am noticing that most of the things in it (with the exception of a bare root raspberry bush that I planted) just aren't doing that well. Meanwhile seedlings that I planted in janky home-made planters left from the previous residents are thriving. Light conditions are the same.
For instance yarrow seeds I planted in April germinated quickly but have now been stalled at the dicot stage with only a hint of true leaves for weeks. By contrast I noticed an errant yarrow seed on the ground is looking much better.
Same with sunflower seedlings pictured -- the ones in the big raised bed are still smallish while the ones in the old planters with the old soil are thriving.
Did I over water? Or will poor quality soil do this?