Corn grows best with warm days and cool nights. Anything from 20 to 30C by day is good. Nights of 10 to 15C are best for high yields. At those temperatures, which are cooler than much of the US, water use will be about 0.2 to 0.25 inch per day. We are warmer and very dry here. Our water use can be above 0.50 inch per day.

If you are just now reaching 30C in z8b, you must be near the coast in the PNW.

Brown bottom leaves usually indicates lack of water and/or nitrogen. Leaves will curl if there is a lack of water. Check the plants during midday. If the color is grayish and the leaves are curling, water more.

Corn needs lots of sunshine and really warm temperatures...75F degrees or more in the daytime [80 to 85 is better] and a fair amount of moisture.

fruitnut thanks for the answer. So I should just give more water, and if it's nitrogen that it needs... what is the best way to give it that?

I am in SW BC.

If the corn is already 6ft tall it is too late to do much good adding nitrogen. If you want to try, add a little of any high nitrogen fertilizer like urea or bloodmeal. Water it in good. Then apply an inch of water for every 5 days without rain.

No, that means 6 inches. 6 feet would look like this, 6'.

I would say you need to feed your corn (you can't do anything about the weather) I would use fish emulsion. It comes in a bottle and is diluted in water and then you hand water. GL.