I also used to have a lot of problems with them. From what I see some series are much better then others. Frank most of the ones you mentioned are from the Big Sky series which were one of the first with a big color selections. Other then Solar Flare I have never had any luck with these. Terra Nova introductions seem to be improving over the last few years .AB cultivars have done very well for me. For the singles go with Pow Wow and Cheyenne Spirit both can be grown from seed and do very well and come in almost all colors.
For your soil all I can say is drainage , I add lots of sand to the mix.
Only feed with a handful of Bonemeal they do not like much food.
Do not let first year tissue culture plants to flower the first season, I know this one is hard so I let them flower once just to see what the flower looks like.
Plant in a raised area where water can not puddle or freeze over them, Causes them to rot.
When cutting down in the Fall leave around 8 inches to protect the crown.
Do not mulch close to the crown to avoid rot.
And I do not plant after July , they need a longer time then most for root development.
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