Cloudy water is often a sign of bacteria. There could be a bacterial bloom in response to the high ammonia. And yes, plecos are known for hurting axies, so that could be part of the problem. The injury pics I've seen were longer rasping marks, not round, but could be. To keep your guys healthy you'll need a water test kit to check for ammonia and other potentially harmful chemicals.
If your tank was healthy for a few months, it's likely you had enough water volume that it cycled with your animals in there, without the ammonia getting high enough to notice damage to them. It could be they were over-fed while you were away and that "crashed" your cycle (meaning too much ammonia was produced for your existing colony of beneficial bacteria to break down), or if it could be that too few water changes or too little water volume for your growing axies has led to gradually deteriorating water quality, and it finally got to a noticeable point. For four adult axies, the general housing guidelines would be to have about 50 gallons water volume to maintain good water quality. I cycled a 50-gallon tank earlier this year with 3 newts in it, and it was a real pain, had to change 20-50% of water every couple days, gradually decreasing changes to keep my water under .5 ppm ammonia readings, and it took 5 weeks . . . Yours will hopefully be faster since it's an established tank. Live plants help, too, by absorbing ammonia and nitrates. There are lots of good caresheets and threads to search on the site, to help you out. I hope your guys will improve quickly!
