Watering plants in Malta - water too salty?

Our plants have always survived on tap water.

I have handed 2 of our plants to the plant doctor below us to get them fixed
Her terrace is shaded most of the day and she uses tap water and all of them thrive.
Ours on the other hand are on the roof and get full sunshine most of the day and none of them are in as good a condition as those kept in the shade.
Cactus love the sun of course.
Could be Gozo water is better than Malta water....
Ray

The only problem we have had is when its been very windy, we have brought our rubber plants indoors.

we grow vegies on out roof and we had big issues when May was nice weather and June was scorching, our cucumbers were bitter and all the leaves went yellow and same with the zuchini and even the tomatoes struggled. we gave them extra food, we use seaweed stuff, baby bio, plus some iron (iron very occasionally) to counteract the high calcium content of the tap water here. remember container planting requires extra feeding than in ground growing. 
they have now adjusted, the last cucumber from the damaged plant was tasty again and our citrus plants and olive tree have had some great growth since we really started focussing on feeding them,
we have now started a new cucumber and its doing great as well as a climbing french bean. we also noticed putting some sphagnum moss and mulch on the soil helps keep them a bit cooler and happier. we also compost all out cuttings and give a sprinkle of espresso coffee left overs (fresh ground not instant) once a month also keeps them fed and healthy.

now the wind of the past couple of days has wreaked havoc and damaged some leaves of the bean and the cucumber

GozoMo wrote:

The only problem we have had is when its been very windy, we have brought our rubber plants indoors.

We are bit exposed to the wind as well even though most of our plants are only 12 - 18 inches high.
I think there is a Clematis up there but it's up a trellis so it's got something to hang on to..