Started week two of my cycle on a 55 gallon tank, tank has 55lbs of sand, two bags were live sand, and about 40lbs of rock that was bone dry when put in. I noticed these tiny reddish brown areas on my rocks. My water temp is 80°F, ammonia earlier was 1, Ph was 8.1, nitrite was 2 and nitrate was 20. I have one power head in there with a basic hang on back filter, which will be upgraded soon likely to a Fluval fx4 or fx6. White LED for now as well. If it’s red slime then what can I do to change it? Some areas (in the 2nd pic) of it are towards the top of tank near the highest portion of flow in the tank.