Grow Mediums This Mix Sound OK?

[I <3 AFN]

You might even nix the coco and add worms like, @Maria Sanchez said, and more perlite to keep it airy. Coco can hold water too, which might not be great in that soil condition, even though it also kick ass at aeration, might be a random time where it doesn't outweigh the cons, especially with the CA/MG deficiency probabilities.