
I am very glad you found your first pleco! As to your question of why your tank is cloudy. Sounds to me like it is trying to adjust to the added fish load.
Most here don't recommend using test strips, they don't give accurate results on your water tests. You won't really know what condition your water is in until you test with a reliable system. I would suggest getting an API Master test kit. then post the results for:
Ammonia?
Nitrite?
Nitrate?
What fish do you have in your tank, and how many of each?
Sounds to me, since you didn't cycle your tank before you introduced fish, you are getting ready for a disaster. Your tank is in a bacterial bloom, which is good in that the bacteria are trying to catch up, but it also means that you are either having an ammonia or nitrite spike. That can be fatal for your fish.
The long and short is until you get the new test kit, you need to be doing between 25-50% water changes every day....
Really take a serious look at taking one of those plecos back to the LFS, if they are common plecos, as they get HUGE, and are really big waste producers. Good Luck