Faulty GPU ports prevent monitor from going to sleep normally

Hello all, 

I am using 2 Dell monitors,

• p2414h connected to an EVGA geforce gt710 2gb via dvi-d.
• p2417h connected to a Gigabyte geforce gtx 960 4gb via hdmi.

The issue is that the gtx960 has 5 faulty ports (3x dp, 1x dvi-i, 1x dvi-d) and the hdmi is the only one that will transmit any video signal.

However the hdmi has another fault. Whenever i turn off the pc, or 15 mins of idleness pass and it sends an off signal to the monitors, the main monitor that is connected to the gtx960 will display "searching for signal. if no signal is found it will go to power saving mode in 5 mins"

Usually when i turn off the pc, i immediately switch off the power strip adaptor. The thing that worries me, is that now when i turn off the pc and i go to switch off the power, the main monitor is still on and not in sleep mode.

Is there damage being done by turning it off like this? or is it ok? Should i turn it off by pressing its power button and then switching off the power adaptor? Is there a way to reprogram the monitor so it goes into sleep mode immediately after receiving no signal, and not waiting 5 mins?

Thank you all for your help!