If you've ever tried to juggle, dance, or learn the steps to an advanced martial arts kata, you'll know what I'm talking about here. You are performing at a high level, you add something to it, and disaster strikes. Within a few tries, you can't even do what used to come naturally.
Writers love courses and book that provide tips and advice. The more, the better. I teach, so I am the last person to discourage this perspective. But trying to integrate several significant new approaches into your writing all at once can be a recipe for disaster.
And those problems are normal. I first learned of the phenomenon I call "dropping the juggling balls" (or dropping the chainsaws when I am looking for danger) when I studied Piaget. It is related to the way we learn and organize new information. When we are little, we go through these fumbles so often, we barely notice them. We just keep on keeping on. But they happen less often for most of us when we are older.
As a result, writers who are diligent about working on their craft can end up discouraged and depressed. I thought I had talent... I thought I had figured this out... I thought I'd never make this mistake again...
No, you are not becoming a talentless, inarticulate hack. You are growing in your craft, and these are the accompanying pains. So cheer up. Something good is about to happen.
Once you adjust your attitude, don't give up learning new skills. But consider resolving to master only one challenge at a time. Focus enables learning.
Writing requires high-level juggling -- character, plot, style, grammar, tone, theme, setting and more. Sometimes they come out the way you want them to all at once, but that is rare. Becoming a master writer is a livelong exercise, so expect to drop a few balls along the way.