Title. myself and my colleague did notice that chatGPT (GPT4) started to answer very poorly in the recent month or so. For example, it was quite efficient at drawing mermaid charts, but not anymore. It fails to do a simple drawing.

Also I've seen quote a lot of posts regarding GPT4 quality downgrade on r/ChatGPT subreddit.

so I guess it's confirmed that OpenAI has downgraded quality of ChatGPT. Whatever that reason is - I stopped paying for ChatGPT and simply use GPT4 API with some ChatGPT interface for simple questions. It's going to be even cheaper for me.