pot problems

Hi all,

a couple of my potato plants, different variety,, the leaves seem to have a brightish yellow legion... only affecting about 5 different plants but wonder wether \i should pull them up or leave them...

does anyone know what this is please?

what are your thoughts on watering? as I gave them a drink last night with the hose but my neighbour suggested that because the ground fairly dry that any slugs/worms would move into the now damp area and then may affect my spuds..

kind of makes sanse to me

thanks all