I'm not so sure about 'lean' for the soil. P. tenx is a swamp-type plant and P. cookianum tends to grow along the margins of bush areas where they enjoy falling leaves and the comfort of their own debris.

Try some compost that has leaf mould in it and mulch with 'bark nuggets' that will produce a moderately acid environment. Our 'standard' nuggets come from Pinus radiata, mostly. You might find that fir bark/cambium will give you the same result.