Hi, تبين = it had appeared that *سوء العلاقات = bad relationship *تدهور العلاقات =with time become worse than before but no a big difference, they give the same meaning in use :)

show, it means that something was found out ( usually when you research something, when you start to explain what you found about you begin with تبين = (تبين سوء= bad, poor العلاقات= relationships سوء العلاقات so it gives you poor relationships/ bad relationships تدهور العلاقات = that's used when a relationship is collapsing or worsening so the difference between تدهور العلاقات and سوء العلاقات is that the first one is a relationship that is changing its nature like i said worsening and the other one is a bad relationship from the beginning. hope it's helpful ^^

تبين means (something has become clear ) سوء العلاقات and تدهور العلاقات don't have a big difference... (سوء العلاقات ) means that there is( poor سوء العلاقات relations) in general but (تدهور العلاقات ) means that the relations (العلاقات ) was good at first then relations became poor and bad ,, For Example You hate a man at first and you still hate him for now (this a سوء العلاقات ) but (تدهور العلاقات ) You loved a man at first and now you hate him