Hi Owen, one thing about neem oil: did you buy the concentrate stuff? I don't know if they have non-concentrated formula available. If you dilute it down, it should last a long time and it's pretty cheap per application. Just a side note in case that's why you thought it was expensive.

As for the corn, usually corn grows so fast that any bugs and most diseases aren't much of a threat to them. There might be an issue with them growing in the bags like they are. They like heavier soil and usually potting soil isn't very heavy. They need a lot of root space and the sides of the bags will sort of prune the roots. They might not be getting enough root space, but maybe someone else knows more about those symptoms.

Hey, thanks for the comment. I got the Ferti-lome Triple Action Plus with NEEM in a spray bottle, $12. Seemed like a lot for one bottle. Maybe the nursery where I bought it marked them up.

I got the design for the grow bag setup from a bunch of Youtube videos showing the same thing with great results. I filled them with a mixture of peat moss, compost, manure, vermiculite, perlite, and ~1/8 cup of Epsom salts per bag. I planted them on February 5th and fertilized them three weeks in with a general purpose 4-4-4 fertilizer. Hope that info helps diagnose the issue.

Here's a link to one of the videos mentioned above: Kiddie Pool Grow Bag System

That's pretty cool. I've no idea what's wrong with your corn but the ppl in that video sure made it work! Good luck.