can anyone tell me what this is.....

[Smells Fishy in Vancity]

just started my tank and been running for a week or so.... after testing the water i realized that i needed to up the pH, so i went and bought "Seachem" Marine Buffer in liquid form. about 2hrs after adding the buffer i noticed a yellow coloration on the surface of the rocks and substrate. its now the second day since it happened and some of the coloration are turning somewhat brown.... can somebody please enlighten me.....thnx

unfortunately i couldn't upload the pics... too large.