My advice would be - stick only to water and ride out the detox. Pray, meditate, rest, relax do what you have to do and remember the crap feeling will pass. Maybe because you were alternating between Master-Cleanse and water fast, the results have slowed down. Remember lots of rest and hang in there !! 25 days of cleansing is a greet achievement !! :)
I think feeling heartburn is normal, I have felt it too (day 18 of water fasting)..