My guess is: your very strong local channels are causing IMD (intermodulation distortion) in your preamp that raises the noise floor from spurious signals generated in the preamp to wipe out your weaker signals, like WPXJ and WIVB which are 2Edge.
WROC and WHUF are very weak Tropo signals that will never be reliable because they are subject to the whims of tropospheric propagation.
https://www.google.com/?gws_rd=ssl#q...ic+propagation
What happens if you remove the preamp? You should be able to get the channels you want down to WUTV without the preamp.