White areas on my euphorbia ?

This looks like 1 of 3 things.

1 A nutrient deficiency

2 A nutrient toxicity

3 Water stress

The first thing you need to do is check the pH of your soil. For this species, a pH of around 6.5 is ideal. You can simple pH kits from nursery supplies places. If your soil is too acidic, it could mean your plant is suffering from nutrient toxicity in the form of a metal, maybe iron, or manganese. Similarly if your pH is high, it could be suffering from a nutrient deficiency in a metal ion, for example magnesium.

To me the pictures actually look like phosphorous overload, but the first step to finding a solution is to test the pH because too high or too low means nutrient availabiltity and supply is changed.

Hope I have helped