IZI Auto Skittles DWC

Last week, rust spots appeared on the upper and then middle floors. I regarded it as a potassium deficiency, added PK 300ppm, but the spots quickly progressed. After a hint in the comments that this is probably a calcium deficiency, I prepared a solution: 60ppm water + 220 ppm calmg (previously added 140) + PK 120 + base. The spots continue to increase, but at a much slower rate. In general, the weight gain is going well, so I don't worry too much)