Hi Gabby, maybe you could try Tea Tree Oil, natural and effective treatment for thrush. Tea Tree Oil is an essential oil with anti-fungal and anti-bacterial properties. The easiest way to use it for thrush is to add 10 drops to 16 ounces of water in a spray bottle. Thoroughly spray onto a clean frog daily.
Mine is prone to frog thrush. Best thing I found - hydrogen peroxide! :) and red horse products (like artimud etc) are brilliant!
I would go with whatever works the best for your horse