So sorry to hear of your loss, My condolences to you and your family!
Keeping discus is not as hard as people make it seem or rather what you read on the web and on forums! 20yrs ago it was hard!!! Now a days discus are so hardy they adapt to many different water parameters. (unless your working with wilds) As long as they are properly acclimated, quarantined, provided with a high protein/variety diet, large water changes and can keep the water clean and pristine you shouldn't have any problems
What i would do is invest in a few more juvies so you have at least 5-6 they would do much better and will be happier in a group that size.
With young juvies you should offer them a hight protein diet like beef heart a few times a day a perform at minimum of 80-100% water change daily with full tank wipe downs till they reach 4-5". If your going to run a canister filter i would use a pre filter sponge on the intake like FMH advised.
I found a sponge that i put on the intake. I made a homemade food that they seem to love. Is it normal for them to breathe really fast? I need to get a few more, the biggest one will sometime chase the other two but not too much. Im doing 50% wc daily and feeding 4x. I feed my mix, bw and beefheart. I use each one daily and my food twice.