Answer: The problem on squash and tomatoes may not be related. Let's take them each individually.
Tomatoes are not commonly affected by blossom fungus problem. It is getting hot enough for tomatoes to begin to have fruit set problems, but if this problem has been going on for a month, that may not explain past blossom failures. It could be a lack of pollination as tomatoes are wind pollinated and a very protected location may not set fruit well. High nitrogen levels can cause vine growth at the expense of fruit setting.
Squash are pollinated by bees and certain other insects.
You indicated that your peppers and cucumbers are blooming. If they are setting fruit, then a lack of pollinators may not be the problem, otherwise it may be an explanation. Squash blossoms are also subject to a decay in the warm days of summer. This usually appears as a decay starting where the bloom attaches to the fruit and progressing down the young fruit.
Remove fruit and avoid unnecessary wetting to decrease disease problems. Fungicides are available but are usually not necessary as these cultural measures are often enough to control the problem. I don't know whether the leaking gas could have any effect. But don't smoke in the garden!
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