change hyro fluid or is it OK found little bit of milky substance (water?)under cap

Got done mowing today and while blowing it off decided to check fluid level in tank and notices little bit of white milky sludge on cap. Now I changed fluid last spring and it has about 28 hrs on it and its kept under a shed so I figure its the humidity here in Georgia. I shined a light inside the tank and it looked ok but I know that's not a really good way to check for water in it. Should I go ahead and bite the builett and go ahead and change or it some moisture collecting under cap...normal? Thanks Oh this is on my 2012 DC Silver Eagle 2760