Saltwater - Cruise - New England (location I think is a key variable, though you didn't ask that). I'm admittedly a cheapskate. I've been in the same harbor for 18 years, and was happy for the first 16 with (relatively inexpensive) West Marine store-brand CPP+ ablative paint... blue. My boat for the first 16 years could just squeeze by on 1 gallon of paint... One good full coat would use about 3/4 of a gallon, and then I would apply the last quart as a second coat on leading edges and near waterline and on rudder... places likely to see the most "wear". I would do this every-other-year, and all was well. I got a new boat 2 seasons ago... and it is just big enough that I need a second gallon... also switched to black (same product though) and while it did a good job keeping barnacles and critters off, it SEEMED to have way more "slime" growth as the summer progressed. No barnacles, no other problems... just unsightly brownish slime visible just below the water line. A little swimming with a scrubby pad/brush removed it (and some ablative paint as well), but this seemed different worse than with my old boat.
Possibility 1: I'm getting old/senile and it was always slimy, and I just don't remember
Possibility 2: With the old boat, I didn't notice because everything looked old and tired... with the new boat, the contrasting niceness of the rest of the boat brought my attention to the ugly marine growth.
Possibility 3: The weather, or climate change, or pollution in my harbor, or a giant-evil-migrating-blob-of-algae arrived in the dark of night and somehow changed the environment my boat sits in, which happens to line up with a weakness in my specific paint's attributes. (Other boats in the harbor seem no better or worse recently, but use various different paints.
Possibility 4: Maybe the black is somehow different... either in ingredients (unlikely), or in how it absorbs sunlight, or is somehow appealing to algae.
Possibility 5: Maybe the guys at the factory changed the recipe slightly... while I searched around and there seems to be no advertised change, that doesn't necessarily mean nothing changed.
Possibility 6: I got a bad batch.
It's not horrible... and as a cheapskate, and non-racer, non-perfectionist, I can live with good performance instead of great... and in all likelihood it is some combination of all 6 of the possibilities I listed, with probably another factor or two I'm overlooking. My advice would be to ask around (which you're doing), but specifically look for what others in YOUR LOCATION(S) are using with success.
As a side note, I painted my prop with Petit Prop Coat and Barnacle Barrier spray paint... and was LESS than happy. While I admittedly didn't fanatically prep the prop to super-smoothness, and that's my fault. I did SOME prep, and there wasn't lose paint on it or anything, and the paint seemed to be a bit pricey, allow barnacles to grow, and chip off in lots of random places around my (folding/feathering) prop. Sure its a tough place to exist as paint... but it didn't do what it said it would nearly as well as I had hoped. Not sure what I'll do in the spring with that...