Hiya Sammy and welcome to Aquariumadvice.
Buncha things to go over.
Firstly, do you have an understanding of the nitrogen cycle? Is the key healthy fish. Do check this article for more info:
http://faq.thekrib.com/begin-cycling.html . How long has your tank been running?
Secondly, water parameters (see nitrogen cycle) are very difficult to maintain in a small tank (such as a 5g). That may be part of your problem. How many fish do you have in there/what kinds?
Thirdly, pH. What do you mean by extremely high? Many of the domesticated fish we get in fishstores are accustomed to pH levels that their wild brethern could not tolerate. Neons for example, do better in lower pH levels, but if they are tankbred they generally only need that really low level for breeding. Also, without knowing what your hardness levels are, it can be difficult to change pH. I would throw the pH decreaser away. My guess is you have fairly hard water; what the Ph decreaser does, when a lot is used, is not change the pH levels until it overwhelms the kH (buffer) levels, then the pH drops severely. Sharp pH changes are MUCH more hazardous to fish then a higher or lower then expected pH. Also read this article:
http://faq.thekrib.com/begin-chem.html
Lastly, cloudy water is typical in a newly cycling fishtank and is a bacterial bloom. It generally goes away when the nitrifying bacterial colonies get large enough to handle the ammonia levels. If the cloudiness is green tho, its an algae bloom and is usually due to too much nutrients in the tank.