Humm you could have new tank syndrome, it is common and if it does happen it will begin anywhere from a few days to a week. Could be from an ammonia spike, from adding to many fish at once. Shouldn't be algae bloom because you haven had the tank up for that long.
Here is what I have done when I have had the same problems with cloudiness, turn the light off don't feed the fish for a few days and cover your tank with a towel so no light can get in. It has worked for me more than once.
If you have a whisper filter or one like it. When you change you filter don't throw the used one away. Empty the carbon out and set the old filter behind the new one. that way your biologicals with go to the new one and your tank wont have to replenish itself. I found that is where a lot of my ammonia and other level spikes were coming from.
What is your Ammonia, pH, Nitrite, Nitrate levels?
Do you have Live Plants?
Have you done a water change? When you do your water changes are you adding water conditioner? freshwater aquarium salt? Most fish even fresh water fish need salt in the tank. It makes them a little happier.
Watch your Pleco since the tank hasn't been up for long if there isn't any algae for him to eat, he will start eating flake and when they do that it is hard to get them to do there job when there is algae in there. I learned that one from experience. I have one that is like that and he is worthless. Algae wafers might be a good idea. But be careful you don't want to put to much in the tank or you might get an algae bloom and that will make your tank cloudy but with a greenish color to it.
Red Tailed Sharks are known to be territorial and they will chase anyone that goes in to that territory so make sure there are some homes set up in the tank. Mine loves tubes. that I bury under the gravel.
I have live plants in my tank and it took a while for the levels to go down but after a few months of battling and water changes almost daily my tanks are fine. I had these fizz tablets for plants and every time I put them in my tank would get cloudy and stay that way for about a week. even with water changes.
Most of what I know I have learned from experience and I hope that some of this helps.
What is your Ammonia,
PH, Nitrite, Nitrate levels?
