It can be a bit confusing - we know! Dr. Pickart as two separate generations of coppers. His first generation is the GHK. They are more fragile and we have to be careful what we apply next to them. When he created his 2nd generation of coppers, he was very careful to make them sturdier! He knew people wanted to use their acids and prescription retinoids with them. Here is a chart showing you what can be used with what.
One more note on copper application - Dr. Pickart prefers Vitamin C and Copper Peptides always be applied at different times of day. This is not just because vitamin C is an acid either. He feels that they can inactivate each other when applied simultaneously. *There is not a study showing this definitely, but we will follow anyways for best-practice. We always want to get the MOST from our ingredient application, so applying them separately is best.
Since Vitamin C is a natural day product and Copper goes on at night for most (that blue color), this is generally not a big issue.