Hikvision image problems

Hi all,

Sorry to ask for more help but just noticed that some of the images from newly installed cameras are struggling with fog at night. See the attached images. The fog looks like erratic rain on the cctv, and keeps triggering the video tamper alarm.

Also, the strange thing is that two of the images seem to have a dark patch on the right side ?

Is this normal ?

Thanks in advance for any assistance.