Did the mineralized soil process about two months ago (thanks Aaron!) and my plants are doing better than ever! The only odd thing I've noticed is if I push on the soil, I get a few bubbles that come out of the substrate cap. Is that normal? All water parameters are good, fish are doing great, plants are growing really fast with great color.
You are probably getting Hydrogen Sulfide gas forming from substrate compaction. Poke at it with a skewer to release it, or you will run the risk of it killing your plants. Trust me...it just happened to me. I also have mineralized in my tank.