[ADTech]

Of the San Diego majors, only 8 & 10 are VHF, all the rest are UHF stations regardless of their original analog channel number.

Upgrading from a 2-bay to a 4-bay might help, but, as TG suggested, you have excessive distribution losses that need to addressed at the same time. Using an 8-way splitter when you should be using a 2-way splitter is a waste of 7-8 dB of signal power. Fixing that problem might be enough to solve the issues. being on the wrong side of the hills from the UHF towers doesn't make things any easier, either. A stronger (higher gain) UHF antenna might be called for.