Can you check the signal strength / quality % level of your antenna signals?
There is usually an indicator showing somewhere in the TV menus regarding TV channel (antenna) signal levels. It may be that either one or the other is on the margin of acceptable reception.
If the signal indicator shows 'weak' signals:
How many 'splits' or different outlets do you have on your TV antenna lead? Unless you have a masthead amplifier to boost the initial signal received, each extra TV point drops the signal level available to the TV, e.g 2 outlets only 1/2 strength goes to each TV, 3 outlets only 1/3 etc.
Has anything changed in your surrounding area between your antenna and the TV transmitting towers -maybe a new tall building in the direct line of sight?
Is your antenna still facing the correct direction and at least looks OK - dipoles not hanging or broken?
Is the antenna Co-ax cable lead still in good condition?
Also some TVs give the option (haven't checked either of yours) that in the event of signal loss that the screen turns to "Blue" rather than showing a snowy picture, so as to be less annoying.
As well as the above, is there also a level check in the menus of your Dish 'box' that you can access to see what the level is?