HelpfulGardener.com

I'm not sure what's happened... my watermelons seemed to be growing fine... and then yesterday I noticed the leaves didn't look right. Today, they all look like they will be dead tomorrow:/
I have 3 plants and they all look the same (they intertwine).
Help!! -1st year gardener

It looks like a bacterial disease, possibly anthrachnose. It is hard to stop. You need to practice good sanitation and in wet humid conditions you need to do preventive fungicides. Since the spores can stick around awhile, you need to make sure the field is sanitized well and to rotate to a less susceptible crop.
https://www.aces.edu/pubs/docs/A/ANR-0809/ANR-0809.pdf