Then there is an outside chance you might have some sort of viral or bacterial infection.
Infections show up when the temps rise, no doubt.
For example, bacterial wilt in cucumbers is spread by the spotted and striped cucumber beetle.
On hot days my cukes would slump like they have not had water for days despite my having just soaked them.
After years of failure with such a simple crop, I stumbled on a cultivar that has strong resistance to wilt, the amazing County Fair cucumber.
Not only is this cuke immune to the predation of these nasty pests they skip over them to attack my trap crop.
And I bomb the HELL out of them with Dawn dish soap and water spray.
Drown you !#$$#@'s!
Most likely your municipal tap water is causing this.
Most communities have adopted the use of chloramine disinfectant.
I discovered this when I moved into my present home, the smell of chlorine just reeked from my faucets.
After about 3 weeks of drinking it I started to get severe intestinal cramping and bloating.
A $40 whole house carbon filter (replacement filters are about $30 and last a couple months) fixed it for me, at least in the smell dept.
I still had terrible results using it for my grows.
In order of preference:
- Rainwater
- Zerowater
- Bottled distilled (88¢/gal)
Chlorine and chloramine are toxic to fish, other aquatic animals, reptiles and amphibians . Unlike humans and other household pets, these types of animals absorb water directly into the blood stream Don’t keep these animals in water that contains these disinfectants. Unlike chlorine, chloramine cannot be removed by letting water sit out for a few days.
https://www.cdc.gov/healthywater/drinking/public/chloramine-disinfection.html
Even though the CDC says chloramine is safe for plants…don’t trust everything from the CDC!
ps That last grow is a beauty!
But something changed since then and I’ll bet it’s your water.
Plus the roots just sit in that water.