Hey tevin93,
I opened up the scene and reviewed your setup.
The only time I've ever seen that warning popup is when an influence is locked. When trying to paint the vertices affected by an influence that is locked, it will not adjust those values per that influence. Therefore a warning populates. That's my limited understanding of how that works.
When I paint weights, I like to weight everything in chunks and then fine-tune it little by little. Locking influences is very crucial to make sure Maya isn't automatically adjusting your weights to un-intended joints (for instance, when you smooth your weights, it will look for surrounding unlocked influences).
So far, everything looks to be fine as far as painting the weights, I'm not receiving that warning. I did notice you have already locked certain influences in the paintWeights UI. I also noticed you're normalizing your weights as "Post."
One recommendation I can make is this.
I tend to use "Interactive" so that my weights are respecting MY values and not spilling over to other joints and their influence. They also obey values between 0 and 100%, nothing above that.
After inspecting your weights thus far using the Post method, the vertices are going above 100% for influence, so your mesh won't exactly operate within the 0-100% parameters. Influences affect them in a different way and I'm not a huge fan of it.
I went to your skinCluster1 on the mesh and changed the weight normalization to "Interactive" and played around with it, so there shouldn't be any difficulty changing its current status. You may see some undesired results at first, but this allows you to control a vertex from 0-100% affected by however many influences the skinCluster1 allows for one vertex.
Using the component editor is phenomenal because you can control the exact vertex weight based on your selection.
You can open that from Window > General Editors > Component Editor. Switch the tab at the top to the Smooth Skins tab.
This will display all selected vertices and show you which joints are affecting them and by how much. GREAT place to start when skinning weights.
Good luck to you, hopefully this helps out a little bit.