Do you have a link to which carbon you use??i had a similar problem very recently, i thought it was my po4, it looks like it was my carbon. i was running rox 0.8 in a reactor for the last several months, my acans used to look good but then closed up simliar to yours and never opened again, once i replaced rox 0.8 with triton carbon (less aggressive) , my acans have slowly begun to get plump

