The brown areas on this stony showed up about 3 weeks ago. I had my water checked all was good but ph was low. I since started using Kalkwasser and the tank as a whole is looking really nice except this digi is still yuck. Ph is at 8.3, temp 76, salinity 1.023. Any ideas? Iodine dip? I did move it from near the top to about 1/2 way down the tank. I also took a tooth brush 2 weeks ago and brushed off the muck but it's come back. Thx all.