I'm on plan S. I've been experiencing different issues— skin rash on my chest, very itchy, sweat smells like ammonia, constant lower back pain (like kidney pain), and I had my period 2 weeks ago, but I'm already spotting. Are all these just detox signs?

Yes indeed and keep in mind that change is stressful, even change for the better.  It makes demands on the body’s innate metabolic process. The rash is probably a “going too fast” for your individual situation. See if the salt & soda bath helps this go away. Otherwise, you should reduce the pace of your work and gentle all supplements down by half.