If Wheat Is Falling, Why Are Calendar Spreads Narrowing?

As I type, CBOT wheat has dropped about 50 cents in 48 hours. But over that period, May/July has tightened from May at 36 cents discount to only 32. So if the nearby supply/demand looks tighter, why is the market dropping? I have to guess it's because other commodities like oil (down $7/bbl over the period) are influencing macro and portfolio investors.

The same dynamic applies to MGEX as well. While there has been a steep sell-off in the outright market, the May/July spread is less than 60% of full carry--and July/Sep is nearly at even money.