Mark Anderson wrote:
I'm having problems with my morning glories this year and I don't know
why or what I can do next year to keep this from happening. [...]

I have a similar situation with MGs on one side of the house where the
bed has about 8-10" of topsoil on top of a sandy gravel layer. This bed
does not retain water very well. The leaves on the MGs have turned
yellowish with brown spots, and are falling off at the lower levels.
They bloomed well though, even when the leaves began to be affected. I
watered this bed frequently, because I was afraid that the MGs would dry
out otherwise.

The other side of the house has a deeper layer of soil on sand, which
retains water much better, and those MGs have gone nuts - they climbed
over (and probably killed) the clematis, are about 12Ft high, and are
blooming very nicely. I did not water this bed as often, only when the
MG's leaves began to wilt slightly.

We're having very dry weather, going into the third week with no rain,
prior to that we had a few good rainfalls in mid-august, but mostly it's
been hot, with some days in the high 20s to low 30s celsius (70s-90s F),
sometimes humid, sometimes not.

So I my guess is that it's overwatering that's the culprit.

HTH