This forum welcomes you and it's great that you are asking these excellent questions. You are right that a rash if it did arise would just be a symptom of detox and that it would be a great reason to continue rather than to stop the fast as continuing would provide the swiftest means by which to eliminate the rash or any other issue of healing crisis, purging whatever toxins are causing it at a maximal rate.
When you speak of enough water i'm not sure what you are referring to, but drinking only to thirst will provide the optimal cleansing and healing environment for your body... including spells of no water when not thirsty however long they may last which could mean days in some people.
The idea that cleansing is enhanced by drinking more water than our body is actually thirsty for is a common misconception (not to say that this is what you believe).
Every best wish for you as you continue in this excellent journey. :/)