I was, as you're probably aware, attempting to figure out if maybe some habit you have could be an issue. Things like using a normal towel, combing your hair while drying, touching your hair too much while drying, all that kind of thing. I have seen some curly's say that It's 10 weights down their curls or that they experience build-up, which can cause them to straighten out or become less defined. But, you say you began using it after you noticed this issue, so that becomes a moot point. The only other things I can think of, at the moment, is that you might be getting build-up from something else and the shampoo you switched to isn't strong enough to take it out.
As for getting your curl back to where you want it. You could try scrunching a curl mousse through your hair before drying, or using a defuser.
On a side note, I now get why you had problems with particular ingredients in shampoos.
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