I suspect that electrical noise interference has raised the noise floor which will mask your weak signals.
Is the coax grounded with a grounding block connected to the house electrical system ground to reject interference?
You can hunt for electrical interference with a portable radio that will tune the AM broadcast band. Tune to a frequency not in use at the low 550 end or the high 1600 end. You can also use the AM radio in your car or a portable radio that tunes the aircraft band which is AM. An FM portable is not suitable for noise hunting.
Your previous thread:
Preamp vs Distribution amp for outdoor FM antenna
http://forum.tvfool.com/showthread.php?t=15963