Does anyone know why my lettuce is yellowing?

Yup some really interesting things have happened in my life since I last blogged.. I got out of bed on many mornings! That's exciting isn't it! I started a new job as a Community Educator, obviously not in the area of growing green lettuces..
I have attended yet another of my courses where I study to work with the subtle energy field (I'd know what to do if that was yellow).... And have planted some things.. Beans on the lattice outside the back door.. Goodness knows I live in a lattice oblong so it needs things to grow on it so's to cover it up.. And the beans are looking lovely. They have purple flowers on there. My Nan used to grow a whole plot of beans, next to her house there was a vacant block and she grew beans. I loved them. I was very lucky and allowed to have my veggies raw on my plate 'cos that's how I like them.. Well 'specially the beans. But my lettuce.. Nope it's not looking good. The passionfruit isn't too bad but those beans..
So Help me if you can I'm feeling down and I do appreciate you... oops I digress into the singing again.. A green and growing lettuce leaf would make a happier blogger. I tried googling for info but it's a tricky 'hit and miss' situation .. possibly I am not super adept at it but there you go you can only give it a shot.
My heavens- the spell check wants to replace my lettuces with lattice that would not be good.. and my veggies with vegas.. just goes to show how you can't trust a spell checker . I suspected as much.