Problem with plants deterioration - complete beginner!

[Greenshoots]

Hi Brains Trust. I am new to gardening and experiencing problems of the kind attached. I feel sure there is a simple answer and was hoping you could help. I have a similar problem with a number of plants in my garden. The leaves start to turn yellow and the plant deteriorates from there. My garden is in Bedfordale in the Perth Hills.
Thnx in advance.

[applestar]

This looks like some kind of a shrub -- do you know what it is? -- but what are the other plants? Even if the symptoms look similar, the cause may not be the same in plants with completely different growth habit or susceptibility.

[ButterflyLady29]

Have you sprayed your yard or the plants with any kind of insecticide or herbicide within the past month?