Is my soil strangling my plants?

Im working on a limited budget to overhaul my yard. My grandmother died and all of it went through about 6 years of no care or treatment. I have started going through and weeding and mixing in soil and planting and pruning. But to be honest I really only know the basics of gardening. The existing soil is a mix of clay and potting soil that is six years old...... like light fluffy clay almost. Ok... So the areas are about 7 feet long by 3 feet, 4x5, and 10x4 (all in feet). I dug about a foot down. I used the soil and manure we already had. So for the 7x3 I mixed in half a 40 pound (2.5 cubic ft bag), and a whole 20 pound (1 cubic foot) bag of manure in. That,s about the formula for all of them. They all got a whole bag of manure. the 10x4 got a whole bag of potting soil. Am I choking them? will they be alright? Too much of something? Whats planted is basics like dahlia and zinnia, some straw flowers, snap dragons and foxgloves. Any help?