Why is Donald Trump declining in the polls?

[Sprouts Farmers Market ✘]

Doesn't look like he's declining to me:

His poll numbers aren't. That is a big lie people are perpetrating based on a couple fishy results directly after debate number #2

However, his favorabilities are basically getting crushed and that should be a concern because he won't be winning head-to-heads with other candidates (and he was never leading Carson H2H)