Euphorbia leaves are turning yellow with patches of brown. Leaves are curling up.

They look wilted and burnt out. The stem seems fragile and week.

Have been giving water once a week since April last week. Weather was cold and have had a few showers in May.

For the last two three days I watered the plant regularly thinking that it needed more water since the heat has set in (June 1-2nd week). Now after 2-3 days more leaves have turned yellow and are wilting.

Meanwhile, there were Aphids on the flowers and on some leaves.

I sprayed oil+soap mix two weeks back. No results. So on Fri, 10th June I sprayed some insect killer and washed off the aphids.

But now the leaves are in sad state. Is it shallow watering? or aphids? or the burns caused by the Spray? or even ... a possibility of Salt build up ???

Please help with needed remedy. Thanks in advance.

Photo link : https://picasaweb.google.com/hemashreesayed/EuphorbiaAmygdaloidesPurpurea#

Here is a link that might be useful: photo link : euphorbia