On a good quality 2 way splitter you have about a -3.5db loss per split. So you lose -3.5db on the first split, will have lost -7db total on sets after second split, and -10.5db total for sets connected after last split.
So that is 0.447 (under a 1/2) of the original signal for tv hooked up to first splitter
0.200 (1/5) of the signal to tv hooked up to second splitter
0.090 ( under 1/10) of the original signal to tv's after 3rd splitter.
If you have signal problems on the TV's you might want to consider getting rid of all the splitters and go with an amplified distribution system like this:
It has adjustable gain, and should allow you to deliver consistant quality video to all your sets, and you won't have the signal loss problems you might have with the splitters chained like you do.
Radio shack usually stocks those in most stores. Which gives you the benefit you can try it out and if it doesn't work out take it back. You would need to plug the amplifier into an AC outlet.