OK, that makes more sense with the splitter used as a combiner for the two yagis. That's what I was worried about. The two yagis might be interfering with each, that's why I wanted you to eliminate the CH 8 yagi for the test by connecting only the CH 7 yagi to the first LNA-200. I wanted you to do that to see if a custom AC7 combiner from TIn Lee would be worth the expense.
Now, before you make any changes to your system, please show me how you are getting power to the LNA-200s.