yep, I'd probably go with temperature stress, you have any shading on the GH? I ask because when my thermometer is in the sun in the GH, the temp can go into the mid 40's. Even in the shade, if the gh itself isn't shaded last week the temps were high 30's. Just remember plants don't like huge fluctuations. It makes them have shock, for example not acclimatising your seedlings before planting out, what has happened to you is the opposite. Instead of taking shock from cold, they have taken shock from heat. First thing a plant does when shocked, is conserve all resources to ensure it's survival so it can recover and still set seed. Typically this means sacrificing flowers and fruit first, and also soft shoots and new leaves, which relieves the pressure on it's food and fluid transport system.
This last week or so we've had has been some quite intense sun. I never burn, yet last week I burnt probably the worst I have for 20 years. (Took my t shirt off for just over an hour to even up my tan) I was still painful 3 days later, and when you consider I visit Malta 4 times a year and have done last 20 years +, it goes to show the intensity of the UV last week here in the UK. That is what has hammered your plants to the point where they have dropped their blossom before the fruit has set. Don't worry it'll set more, just be mindful of the temps in the GH, and also shading. Good luck.