Can someone who is envious (the object of envy) differentiate between self-inflicted envy and envy from others, and what is the cure for each?

If a person admires something he possesses and does not invoke blessings upon it, and then that thing is affected, it is possible that he has envied himself. It is not possible to definitively identify a specific person as the envious one unless the effect is direct, immediately following an expression of admiration and the failure to invoke blessings. There are unlawful methods to identify the envious person, such as imagining them during recitation or seeking assistance from jinn. These are forbidden diabolical acts that cause enmity and fear among people and fall under seeking assistance from devils, which is prohibited by Islamic law. As for the treatment of the envied person, it is through legal ruqyah (definition) and remembrances, or by requesting the envious person to wash themselves and pour that water over the envied person if the envious one is known.