Lettuce yellowing

I have a raised bed on stilts with compost in which I planted some cos and red lettuce. I feed with seaweed but apart from not really growing much, the outside leaves of the cos start to yellow and die. Some have just rotted to the core. I pull them of and the next layers go the same way. While I am at it, the newly planted rocket and spinach have bolted already. I keep the spinnach in the shaded area of the bed but it still doesn't seem to like it.

My newly planted rocket and spicey leaves bolted as well, I'm sure I only did them three weeks ago.  Pain isn't it.  Some of my lettuce has done the same as yours as well.  I didn't know they don't like too much fertiliser, that could be my problem.