Thank you for your question. After any surgical procedure, healing generally can continue to occur for several months until maturation of the scar and wound. This is typically reached by about one year after a surgery. Without seeing a picture, it would appear that your wound was either...
Swimming in a pool or hot tub is not recommended unless the wound is epithelialized, or else you risk infection of the wound. Raffy Karamanoukian, Los Angeles
It is impossible to tell exactly what is doing based on that photo. I would consider Tinea Versicolor, which is caused by a yeast, to be a possible cause.