Very good question.
Your mentioning the duration of the symptoms of random yellow bruise marks and lack of breath and mentioning any other symptoms would have helped me.
Anyways, the yellow bruise can appear due to sudden loss of weight as such called as striae.
Since you have a doubt, it is better to get the blood tested in this regards.
Leukemia is not that easily picked up, good that you thought about it.
Hope this helps you.
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