Your plants look very vigorous! In fact, your query isn't really about starting them off so much as about the quality of the cobs.
Maybe you harvested the cobs too late. When the silks are a nice toasted colour, I peel the husk back a little bit and compress a kernel or two. If they exude a milky-looking liquid,the cob is ready. If the liquid is watery, carefully fold the husk back into its original position to prevent pests from getting in and leave to ripen for longer. If the kernel is 'doughy' (according to Joy Larkcom), the cobs are past their best. If the cobs were pretty well full of developed kernels but just not nice to eat, you probably didn't pick them at the right time
The other possibility is that the female flowers didn't get pollinated by the males. If you had cobs with only patches of kernels, this would be the case. I once had no kernels whatsoever as bees took all the pollen from the male tassels. One option might be to grow more plants to increase the amount of pollen available or you could hand pollinate.
I have only once hand pollinated sweetcorn. I snapped off some male flowers and shook and tapped them to release the pollen directly onto the female silks. I did this during another bee invasion but it was only partly successful. I should perhaps have repeated the operation as the lower female silks were perhaps not as ready as the ones at the top. Other people will probably be able to give you better advice.
The other thing is the number of cobs. Even though my plants often make three cobs, in fact the third one is never a great success. Some people recommend removing the smallest cob so that the plant doesn't waste energy on it. If you do this, use a decent pair of secateurs. I was surprised how much damage I managed to do to the plant when I tried just snapping it off as I would a ripe cob.