Burn marks (Rust spots)

Good day everyone, I trust you are all doing well. I've recently switched to a different soil brand due to availability. However, upon planting clones in this new soil, I've observed the development of rust-like spots on their leaves. Interestingly, the mother plant, which remains in the previous soil, exhibits no such issues. Can anyone offer insights into potential causes for this discrepancy? Thank you in aadvance

Need more info. What soil is that and what did the clones roots look like. I would foliar feed calcium but that may not fix, and may not even be the issue. It looks like typical calcium burning but that can happen from different things