It is really a puzzle for us.
It can’t be a temperature problem. Plants that you have been trying to grow are not heat sensitive- they actually favor warmth.
You first patch may have been rotten indeed, if the water level was really that high.
What about the water quality? Is you tap water generally ok and drinkable?
Rosemary though needs at least three weeks to sprout. How long has it been now?
I would like to encourage you to try again. I understand it is becoming frustrating, but it will be super rewarding once the plants start to grow.
Let’s figure out what is the problem, because that high failure rate is not normal and we would really like to learn what is causing this.