I planted mini pumpkins and have 2 healthy lil guys that I picked. I think I might have made the mistake of looking online for the care of pumpkins. It said give them a lot of water so that’s what I did. It may be a coincidence that we also have had an extremely hot summer but now the leaves are yellow and a lot of vines have turned brown. The vines are flowering but I haven’t seen any pumpkins produced lately.
Hi- excess water would only be a problem in your bed if the soil remained saturated with water for days at a time (depriving roots of oxygen). Plants would typically wilt and decline under those conditions.
Even with mini pumpkin it's not likely that the plants will have time to produce full size fruit because days are shortening and sunlight is less intense.
We can not say for sure from the photos what factors led to lower than expected productivity. Squash and pumpkin vines naturally decline late in the season with leaves yellowing and vines withering. Tight plant spacing, low soil fertility, weather extremes, drought, lack of pollinators, are some of the factors that can affect plant growth and fruiting.