Duh duh duh! algae rid? i havent read the full label on the algae rid products, but perhaps there is a warning not to use with soft water as it will cause a ph crash due to insufficient buffer...
Also dont use KH up, once again it is just temporarily chemically altering your water, and everytime you change some, youll need to adjust again. buy a whole bag of crushed oyster shell and either put it in your tank or filter, put enough in to bring your KH readings up to about 3 degrees and you should be fine.