Did the doctor test you or treat you for a yeast infection of the tongue? The itching makes me think this. I'd get swabbed for that to make sure. It's common and easily treatable if you have this.
You can also brush away top layer of tongue and leave red like you describe in middle if you were doing that
I did read about vitamin deficiency and red on tongue.
Anayway, I'm still wondering about yeast on your tongue. Not thinking the body itching is related to the tongue though.
I'm tossing a dart in the dark on this one. First off, medicines are dehydrating as heck.
The human tongue has a habit. A big one of showing hydration, the human body it also reacts and pinpoints areas in serious need. Your throats dry? Your tongue is pink exposing moisture and bringing moisture to the first area to effectively solve the problem. Yes, I'm going to say it. Drink water. Lots of it, not at once and believe you resolved the problem instantly that your body has with your daily liquid habits. Soda coffee, alcohol etc...
All of your issues had a commonality though. "Dry" Lotion isn't going to drastically improve your skin "Literally the human bodies largest outside organ
Just personally saying. Hydration is hydration and don't knock water. It makes up 60% of our physical bodies. Incorporate it, a lot for a while. Also avoid, salts, sugars, caffeine etc... like really I'm prescribing water here. lol