Beer Head Question

I keg most of my beers and love it. Unless we have people over, I am the only one who drinks them (SWMBO doesnt like beer ) so sometimes it's days between pints being pulled from a given keg. I have noticed that if the beer sits long enough without me drinking any the first 1/2 pint will have a head like the first pic below. After that the head is like the 2nd pic. Does this happen to other people? Is there anything I can do to avoid it? Would better quality beer line help? Right now I've got the basic 3/16" beer line from Keg Connection. I know the obvious answer is drink a pint of everything on tap each night. I could potentially do that now since I only have 3 on tap but I plan on having as many as 6 or 8 in the future so that's not gonna happen

Haven't had that happen but my shot-in-the-dark would be: dirty keg lines or tap. Maybe the beer is gunking up the lines. The first pint clears the crud, the second one pours better. Check the lines before this happens again.