Yes, you've finally found the right place hopefully, so welcome to TFF!
You've got fish in there, so the problem is urgent. You'll probably need to perform an immediate 50 to 70% water change (assuming you don't know your tap water stats for ammonia, nitrate, etc., but tell us if you do). The return water needs to be treated with a dechlorination/dechloramination product (we call this a "conditioner") and roughly matched to your tank water temperature (using your hand is good enough.) If you need help with the physical aspects, siphons etc., just shout and the members will give advice.
Meanwhile you need to plan to quickly get a thing called a test kit (assuming you don't have one already.) Most of us use one called the API Freshwater Master Test Kit, which works really well, but there are others, the Nutrafin Mini-Master is another good one. The test kit must be liquid-reagent based and test for Ammonia, Nitrite(NO2), Nitrate(NO3) and pH at a minimum. A test kit for KH is also helpful if you see one and are not strapped for money (or you can wait on that.) OK? So be planning that trip to the store, or the online order or whatever.
Additionally, you need to "start your education", which will be the most important thing in the long run. Please look at the pinned articles at the top of the "New to the Hobby" forum and plan to read as much as you possibly can. You should start with Beginners Resource Center, Cycling Resource Center and be sure to look for articles by Miss Wiggle and AlienAnna. Then be sure to read our main working document on Fishless Cycling by RDD (rdd1952) and don't worry if you don't understand all of it, you'll have to re-read it later anyway.
Don't worry if all this seems weird. It did to me too and to many of us here, but its the real thing and thousands of times better than any advice you'll get in a store. At least you don't sound like you are overstocked, at least at my quick glance. Regardless of how well your tank was running the first 2 months and whether it cycled, it sounds like you probably killed all the bacteria in your filter by cleaning it with tap water and now you are in what we call a "fish-in" cycle, which is not a good thing, but can be handled with knowledge and a lot of hard work doing many water changes. The members here are great and they will take care of you!
~~waterdrop~~