Our butternut squashes invariably look like this every year, probably in our case because initial growing conditions are not ideal, viz. window ledges. Although each plant is then put out eventually on a soil mound with a dollop of well-rotted manure underneath they can sit there for best part of a month, not knowing whether to live or die, before eventually getting a move on.
So I would not worry too much. You could try a foliar feed or two in an attempt to get them going sooner.
