You may have overdosed with chlorine control.You should have left them behind the filter.They need a place to hide and it sound's like they could be stressed because you don't have enough cover.Put some plants and ornaments it.
Get the same in Devon as do my mates.Mainly BBC.It's because we have to
put up with it until the BBC switch to full power when the big cities get turned
on.You go to first time installation again.It also helps it you first pull the aerial
out until it has gone half way installing then put it in.