All but your blueberries should do fine in plain potting mix. The blueberries need a more acid soil and mixing the peat with the potting mix (about 1/2 each) will help in that respect. If the hydrangea is one of the mophead types (and can change color), then making the soil more acidic (and adding a little aluminum compound like aluminum sulfate) will help the flowers to change towards bluish. Otherwise they tend towards the pink with neutral to alkaline soil.

Hollytone is a natural, slow-release fertilizer that is usually directed towards acid-loving plants (like blueberries or hydrangeas), but can do well on most anything. Bonemeal is a natural phosphorus source and can be used on any of those plants. I usually fertilize about now when plants are leafing out and then a small amount in summer and some more in fall (about every 3 months). That extra summer boost is because in containers, the fertilizers tend to get washed out more than if the plants were in the ground. I try to use the slow-release ferts like Hollytone, Plantone, Osmocote, etc., so I can add it and forget it for a couple months.