Think of a maize crop in a field - it's way taller than yours, so be patient. It looks healthy and if we get some sun you'll get cobs, all in good time. If not, start them off in big pots indoors earlier next year, plant out carefully. That's the great thing about gardens - if it doesn't work one year, try again next year
I grow mine inside my polytunnel (S Scotland, at 1000', cold and windy). When I have tried them outside, they never grew as big or as healthy as yours, just small and yellowy, so now it's always indoors. My current crop is taller than yours and I've not noticed anything developing yet.