Fixing moulding cracks on porch & Paint chip

We have a Irving model in Southern Walk and it's past our 1 yr.

I noticed we have many cracks in our Moulding above our front door, and above the steps. These are straight cracks. I am not sure who to fix them because they look like crud. Can I get something that goes into the crack and then paint over it?

Second question, The railing on our porch has paint that has come off it - leaving a blueish hued color under the white paint. I hosed off the porch in the summer, but cannot understand how the paint just washed off like that. I also have paint gone on the frame of the windows by my front door. Should paint come off that easily in a years time? Can I just paint over it?