Glad you found the problem. I was actually going to respond and agree with Korkscrew that it probably wasn't a protein problem since you're processed, but you figured it out.

HWP is a big nono for me personally and I've never heard of it being considered a more moisturizing one,
but I really don't know as I avoid any obvious protein.

It would help if we knew the thickness of your strands.
If your hair is fine and low-porosity then from what I've seen theres a big chance that your hair is not protein sensitive.

Also depending on what kind of products you use (are you fine free?) the problem just could have been build up - if not silicone then protein.

If it was not build up then heat should really help your DCs.