Kath, you may need to buy an outdoor guage..this will tell you if the soil is acid or neutral. Aside from fertilizing, (I do this w/acidic houseplants) use an old gallon milk container, 1 capful of vinager, and water. Water each plant w/the vinager mixture.
As for cold, you can try mulching about 1' up..Some ppl use Christmas tree lights.
Please do not overfeed..This can cause death upon plants..Toni