[@Raijinslayer]

Why you ask questions? Why you make difficult?

Honestly, I have a much different theory than you guys which I have stated more than once so not really sure what direction we are going to go in.

I think that the corrupted gems are born that way, that it is an actual problem within the gem itself which is why Rose could not fix it because it isn't like a crack or something. This virus/corruption is in the DNA/Chemical make up of the Gem itself and thus the healing doesn't recognize what needs to be healed. This is way when the gem goes into a basic shape it is human, the glitch or virus can't add human details and has to do a different creature or has a picked creature. (I find it funny that they look like things found on Earth most of the time)
Either that or the virus was meant to make them like creatures so they could use them when the war broke out. It could honestly just be that they didn't get enough nutrients or were formed way too early. I just find that the injectors to make gems are in the same form as a virus.

I don't think the corruption is mental state for one very important reason. Lapis has a base form and only shows details of one form. Peridot has base form and only shows one form for details.
Centipeedle, base form is human like all others but the first details form is the large centipede look. It noticed Steven's reaction and thus changed its detail to the smaller one. Not once did it show a human detail before the large centipede form.