Corn not growing

Clay soil has a lot of nutrients in it, but corn (like most grasses) uses nitrogen. I would apply it, but something like Miracle Grow according to the label directions. Rotate your crop next year and prep your soil by tilling in compost (or any organic matter) and

One thing of note is that corn will not form properly unless there is a block of at least 4 rows. A "block" should contain at least 10 plants per row, with 4 rows. This is required becuase corn is wind pollinated and needs a good bit of pollen to get it to developing. You may still get some corn without this, but much of the corn will not form properly, with many undeveloped kernels on each ear. Planting more than one variety is not generally a good idea, unless as you've mentioned one is early and one is late. If they were to come to tassel at around the same time you could end up with a number of deformed ears as a result.

And as already suggested corn is definately a heavy feeder and required a good deal of nitrogen. Dried, pre-composted manure is considered a very good fertilzer for corn. Fresh manure can be used as well but is not generally reccommended...

I know that you are a stupid troll that knows nothing at all about gardening, Broccoli!