Woa 1077 way to grill the OP...
The OP is simply looking for a nice single pair to house in his 135. The mayans were not working out so he went with the festae. I don't think he plans on keeping them all together long term anyway. I do think he should get more than 2 because one will most likely be killed. And it is not true that responsible fish keepers seldom loose fish. I know many very experienced fish keepers that have trouble with some fish. Festae is one species that comes to mind. They are highly aggressive toward their own kind and some people go through many fish before they get a compatible pair. It is not because they are "irresponsible" but simply the nature of the species. I know from experience. I have a pair of cubans. I originally had 5 but they killed eachother off to a pair. Cubans have very high conspecific aggression so sibling casualties is common. I take good care of my fish feeding them quality pellets and performing 50% water changes weekly. And this was in a 125 and the cubans were no more than an inch or two long. Aggressive cichlids are hard on each other and other fish that's just the way it is. I do not condone keeping several large aggressive fish in a small tank to watch them kill each other but I understand that sometimes causalities happen when trying to get some of the heavy hitters to get along in a large aquarium. I don't think the OP is putting them together to watch them fight. He has simply been unfortunate in getting the mayans to cooperate.
To the OP festae are very hard on each other. A pair may form and get along for years then the male snaps and kills her. It happens. Know you may go through several fish before you get a compatible pair and even then success is not guaranteed. They are also very slow growers so it is a slow and long process. Be prepared. They are gorgeous fish when mature though and look stunning as a pair.
Sadly ,it is largely,nearly alway's, the uninformed,misguided,that lose fishes.
Those who research ,plan,seldom lose fish for they are fully aware of what is needed for the fishes longterm,healthy existence,survival.
Large tank's to hold fishes like the fish mentioned between mating, so females can rest, to seperate aggressive male/female fish, or to seperate Fry for growing out .(Even fry can become aggressive,more tanks).
Plans for selling, or housing the offspring if that is the goal, (not many taker's for large aggressive fish).
Tankmates that are able to defend themselves .
As mentioned ,large enough tank's 200+gallons for keeping more than a pair of species mentioned.(this is key)suitable decor and lot's of it to help curb territorial disputes.
No need to go through several fish as you mention, if Research, plans, are made in advance (spare tank(s).
Have kept these fish, along with Parachromis Dovii,Managuense,Buttikoferi,Trimaculatus,etc when I was much younger.(Yes,I lost many ot of ignorance)
They are very hard for many to care for properly, and trying to place a pair is indeed difficult.
Would in my view, need several juveniles ,with plans made for those that Male/female reject's.
No need to place a bunch of fish in the tank to be killed ,tore up, while trying to find suitable mate, but many don't plan, and sadly,, ,that is normaly the outcome or,,fish are released into streams,lakes,once they become too much for hobbyist's to care for or they become bored with large tanks with but one or two fish.
I personally love these large cichlids and am just offering some words from expierience for other's to consider BEFORE,, more of these fish are flushed,tossed,killed,due in large part from failure to research,plan.
Some fish, such as those mentioned above just can't be housed with other fish no matter how well we plan.
They can still be quite a site as specimen only and with proper care,provide year's of enjoyment.
As single specimen,,they don't need quite as large a tank.