1. throw away your shower shoes...they are cheap.
2. Wear cotton socks, change them every time you eat and use powder.
3. Use a hair dryer to dry your feet out of the shower, be sure to get between your toes. Take your time, if you rush, you won't get cured.
4. swap out your shoes / boots / whatever you are wearing to allow them to dry at a minimum for a day between nastyness.
Fungus likes three things: dark, warm, moist...it must have all three to survive.
Peroxide is a great cleaner for your feet, it changes the pH to an unfavorable environment for fungus to grow...just use the hairdryer afterwards.
If you still are faced with this...can be two other things...
1. Erythrasma: a bacterial infection that will flouresce coral red under a woods lamp
2. Yeast: yes, yeast is a kind of growthy thing, but you should take meds orally to assist in getting rid of it.
in ANY case...watch for secondary infection and cellulitis...if this appears, see your doctor sooner than later.
Good luck
Eagle