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You won't be able to know until you have the water tested. This will let you know what is in there, what to add, and what to try and remove. Depending on the type of salt, and amount, this is what is likely killing the plants.

This link will help you to find your closest extension service. They will be able to test your water and tell you what is in it: https://www.gardeningknowhow.com/extension-search

If it's a short time, less than 2 weeks, you can create mini terrariums. For longer periods you may need to solicit help from a friend or relative.

https://www.gardeningknowhow.com/houseplants/hpgen/while-youre-away-vacation-care-for-houseplants.htm

Unfortunately, this is very plant specific. Simply put, some plants will require more water when flowering, while others will require less, or even none, while flowering.

This article will give you a general idea of watering houseplants: https://www.gardeningknowhow.com/houseplants/hpgen/how-to-water-a-plant.htm

Generally, a plant will want the soil to increase in pH slightly, which comes with an increase in phosphorus and potassium, or a decrease in nitrogen content.

Combined, the ratio change of nutrients, along with many environmental factors that are plant specific will dictate flowering in any given plant.

These articles will offer more information: https://www.gardeningknowhow.com/plant-problems/environmental/plant-not-blooming.htm

https://www.gardeningknowhow.com/special/children/how-plants-grow.htm

Generally it does no harm; it actually can benefit some crops. Here are some to avoid that may be sensitive: apple, apricot, blueberry, currants, gooseberry, grapes, pear, brambles and vine crops.

Problems can include scorching of leaves, dwarfing, dropping leaves, and less fruit. Do not use sulfur when temperatures are above 80 degrees Fahrenheit (27 C).

It isn't going to hurt your houseplants at all, but it won't be a complete nutrient regimen on its own. Combined with fish waste, it can be a good fertilizer water.

This article will give you more information on watering with tank water: https://www.gardeningknowhow.com/garden-how-to/watering/using-aquarium-water-for-plants.htm