they infected the whole garden

==>>> the odds are so low.. as to be infinitesimal ...

you need to define the problem ... specifically ... and then react accordingly ... it could sun... zone inappropriate plants... hail... vermin ... lawn ferts.. lawn weed sprays ... jeez.. just about anything .... dont suppose you have some pix??????

but at a min.. remove the problems... and replant ... or perhaps let that spot lay fallow for a season ...

if boiling water makes you happy about it all .. go for it.. cant harm much else ....

yellow spots on leaves.. can be so many different things .... its hard to provide any real info.. to help you ...

ken

Hey you're the same guy, hi , well even if it's not infected i want to start from scratch, and im new in this so i dont know much, anyway, here are some pics

and another :

I wouldn't worry about those spots, personally. They just look like old leaves at the end of their life cycle and don't look like a danger to anything. The plant in general looks quite healthy. You can pick the yellowed leaves off if you want.

Gardens are not perfect. If you are going to "start over" every time a plant has spots, you'll never have a garden. Plants get pests, diseases, get thirsty, etc, etc. Old parts of the plant die and fall off. It happens, it's nature. The majority of the time, these things will not ruin established plants.

As a gardener you will also have new plants die. Gardeners with "green thumbs" have lots of plants die, but they keep growing and planting, and they learn what they like and what likes them. Many times I don't even know exactly what killed a plant. I just move on and find a plant that does better.