Try dilute h202 in a foot soak. Then spray on Colloidal Silver and let dry . The silver residue will inhibit fungus. Also wash socks in h202 water and then rinse in Colloidal Silver added to rinse water. This will leave a silver residue in the socks which will inhibit fungal growth.
Then spray some Colloidal Silver into the shoes for the same reason.
Also look to your diet to get your biological terrain turned around.