Definitely looks like ammonia burn and it is solely a water quality issue. Since you washed out your entire filtration system which I strongly suggest to never do that again, it is safe to say you have killed off your much needed biological bacteria. Hopefully, you have not done the same with your substrate in your tank and still have some good biological bacteria left to replenish your system fairly quick. You will most likely experience a mini cycle at best which will mean more ammonia and nitrites too come so I would be using "prime" to bind it to a non toxic state and continue with 25% water changes daily(add prime with each water change) and add salt to help with gill function until your system is stable.