Erosion is what I have been leaning towards but there aren't any inclusions in the casting nor does any debris fall out when I blow off the bottom of the flask right before casting. I was thinking maybe the investment is not curing or hardening enough in the oven? I did two test casts by leaving the flasks in the oven for a tad longer. On the first flask the sides of the class ring (the numbers) came out perfect, but the letters on top still filled in. On the second flask it came out looking the same as the images above. I am just at a loss because all other pieces, that are in the oven along side the class ring, are coming out fine.
A little more info on my casting process. My ratio for the investment is roughly 40ml/100g and the flask usually sit for about 6 hours before they go into the oven. The oven times are 300F for 2hrs, 700F for 1hr, 1350F for 2hrs, and then 1hr soak time at casting temp. The flask themselves are either 2.5x3 or 3x4.