Decreasing capacity of plasma cores

Hello all. I'm pretty sure that everybody has the same as me. I'm playing a lot with my Gatling Plasma. It's fully modded (but I noticed doesn't depend on mods). Example: I've got 20 Ultracite PC (500 capacity). Suddenly, some magical thing happened and rest of my PC have only 375 capacity. I don't know when but the only way to fix it is to throw all PC and make the new ones (500). Do you have solution for that? Thanks in advance