what you need to look at is distance in miles, signal strength and noise levels. also LOS or line of sight if you could save the image post transition and attach it I might be able to see if there is a problem. although if you are getting all on the down stairs converter, then it could be the runs to the other converters that is hurting you spliters will drop your signal 2.5db per out put so if I were you iI would get a one in 4 out distribution amp and put it on the backside of any other pre amp you might have and see if that helps. you could also change all coax to quad shield which has less signal loss and rejects more noise. make sure that the coax does not run close to or over any electrical lines or light fixtures.
