If your LCD / LED TV are having black cloudy spots, the problem is coming due to dust ingress inside the panel of LCD / LED TV or monitor most probably. The defective TV clouds may looks like as below:
Normally TV Monitors are perfectly seal tight, so ingress of dust inside panel is very rare. Sometimes some TV panel are not perfectly sealed, in such type of monitor, there is chance of dust coming inside the panel. Dust inside panel sometime causes black spots cloudy screen. The clouds on screen is more visible when you see perfect white photo or picture on TV Panel. This problem can happen any any TV model like Samsung TV, LG TV, Sony TV etc..
To get rid of this problem, panel is required to be changed. If your LCD/LED TV is on warranty period, you will get your TV Panel replaced free of cost. If your warranty period is over, try to get is corrected in service center, service people will most probable say they can not repair it, but if you try hard they will be agree to repair.
If they will not agree, then you need to buy the new Panel, the cost of new TV panel may be half of the price of the TV. You should not try to clean the screen or repair the screen TV panel, it may damage the panel permanently..