My 5 yr old female mastiff had yeast infection in one ear for 3 days, was treated and infection is gone but on 3rd day she started having diarea witch has lasted 24hr's so far.she is drinking lots of water and is still eating fairly normal but is panting a lot. I'm getting worried,any ideas.

The only valid answer is to see your vet. We can't diagnose online, and a dog as sick as yours, needs to see a vet.