Ssuarkc - Epsom salts (MgSO4) are high in Mg, so if you suspect a Mg toxicity, why would you add more? Since an excess (toxicity level) of any nutrient has the same limiting potential as a deficiency, an excess (toxicity) of Mg (or any other nutrient) can "make your plant sick". Are you sure you didn't read it was a (P)hosphorous deficiency (rather than a Mg deficiency) that has some considerable potential to cause purplish foliage? The most common cause of purple leaves (very common at this time of year) is a deficiency of phosphorus (P) because P is required to make ATP and ATP is needed to turn sugars to starch and to load sugar into phloem for transport. No P - no ATP - no move sugars/starches - anthocyanin (purple pigment) builds up - plant turns purple. The most frequent cause of a P deficiency is cold soils, which is why so many plants planted out too early turn purple. A P deficiency is not the only suspect cause of purple leaves. Nearly any environmental condition that puts the brakes on growth and the accompanying use of sugars, but does not limit sugar production (photosynthesis) can cause anthocyanin buildup and purple leaves. If only the outer edges of the leaves are purple, it may be a K or Mg deficiency. If the center of the leaves are also purple, it could be too much Ca in the soil or the result of too much water in the soil blocking uptake of P and Mg. Do not apply a fertilizer with the middle number higher than either of the other two numbers (N & K) to container plants. There is never a need for that much P (relative to N) in container culture unless you're supplying only N in another form. Plants use about 6 times more N than P and the massive doses of P in 'bloom-booster fertilizers' cannot do any good. Al

It may be Cryptotaenia japonica f. atropurpurea

Panicum Shenandoah has red highlights in the foliage almost from the beginning of the season, with the red increasing with more weeks of heat, and then getting a further boost in the fall - at least here in southern NH. The red color is heat-driven, so there will be less of it in cooler years and/or cooler climates. It's a definite beauty here for folks who want the deep red.

Hydrangeas require some sunlight (morning or late afternoon, often referred to as "soft" sunlight), to bloom well. The macrophyllas (yours) also require an even applicaton of moisture during their active growing season. It is generally agreed, that the requirement is about 25mm (1 inch) per week. Those grown in containers will require more, due to the small soil mass and more rapid evaporation. With higher ambient temperatures, more evaporation will occur through the foliage (to keep it cool) and moisture requirements will escalate. Fertilization and frequency varies with location. In your area, addition of a slow release, balanced fertilizer can be applied twice each year, early spring and late summer. Rooted cuttings can benefit from a formula with extra phosphorus. I use a water soluble, 15-30-15, type during the first year of growth and after that, only an annual application of compost and/or leaf mold on the root zone. Don't know about prices of chemical fertilizer in AU, but the worldwide demand, especially in China & Africa, with limited supply sources, has driven up the price in the US to a point that it is almost unaffordable. Thus, my attempts at organic gardening, both ornamental and vegetable! Rb