After substituting CaCl2 with CaSO4 for a couple months, all my plants are doing well with no signs of melting or stunted growth. As a result of the increased growth, I'm getting almost no signs of algae now. All my parameters are exactly the same, so I can only blame the Cl. But, of course, more testing is required to confirm this. It did take a while before the improvements kicked in, approximately 2 weeks or so. So, a bit of patience was required.

Thanks again to JoeBanks for the suggestion!