CichlidFish.com - Fish That Think.

I had to replace my red devil that recently died. He was in a 75 gallon tank by himself due to his extreme aggression. Today I purchased a flowerhorn, jack dempsey, and an Buttikoferi. All three of these fish are juvinile and get along great. Due you guys think I will have problems in the future? Overall I am very happy with these guys as they add so much color to the tank.

Well, in a word, yes.  That buttikoferi is at least as much of a handful as your red devil was. 

Hard to say, From what I'v read both flowerhorn and buttikoferi get quite aggressive and large.  And with the jds its a toss up I have had one that was a killer (went through 3 females before i gave him away) and that was still a small jd only 4 inches and one of the females he killed had a good 2 to 3 inch bigger then him.
IMO you will nedd a much bigger tank to keep all three,  but I may be wrong.  Ether way have a back up plan ready just incase things go south.
Here got board and looked up adult size ,tank rec, mates. ect, per one of each for you:
 Flower Horn: approximately12 inches in length, Co-existing with other fish is not advisable, especially smaller fish
                    79.25 US Gallons is the minimum. I`d keep 1 Flowerhorn in a tank of at least 158 US Gallons.
 jd: 12 in. very aggresive most times but some are fine with fish of same of larger size and aggrestion (Note they   love caves) 55 gal min atlest 75 with tank mates More hiddy hoels the bitter with other fish.
Buttikoferi Cichlid:(note is affrican not american like the other two witch alone can cause problems)
                       12 in.   Aggressive,  Minimum Tank Size: 70 gallons.
Look up more info on the net and be ready from what i read to get this you are in for one bloody battle if you dont get a much bigger tank.
See what every one else says though.