AHhhhh!
First of all your tank is not cycled. I dont know how this happend being that you used an established filter and its been 3 months.
Did you add the fish as soon as you transferred the filter, or did you wait a while to add fish? If you weren't feeding the bacteria then it most likely died and the cycle will have to start all over again.
Okay... so you have a 29 gallon tank with fish that are wayyyy too big for it. The only fish that might be okay is the 4" lace catfish. The rest are much too big.... and the flowerhorn is only gonna get bigger.
You feed 2-3 times daily!? <----- Possible (likely) cause of the cloudy water and uncycled tank. I feed my fish minimally once a day.... and skip a day every few days. Fish do not need a lot of food!!!!!! They eat minimally in the wild... so you must feed them minimally as well.
Personally this is what i would reccommend:
Beacuse your fish are too big for this tank i would take them all back and start again. Do a complete clean-down. Refill tank with new water. Start from scratch and either do fishless cycling or cycle the tank with a few danios. Read up on cycling to be sure your doing it right. Dont feed your fish so much! Instead of doing big water changes every once in a while... do frequent little ones. Ph seems a bit low as well.... but that can be worried about later.
With a cycled and healthy tank you should NOT be showing ANY Ammonia or Nitrite.... and Nitrates are removed by doing weekly water changes... and you should not let them get too high.
If you dont want to do the complete tear-down i would just fast the fish for a couple days... then start feeding them less. Make sure the pleco is getting algae tabs and what not. Continue with lesser and more frequent water changes.... and see if this helps the cycling and the cloudy water.

-Diana