Are you using strips or test kits for your ammonia and nitrite testing? Test kits are much more accurate than strips. I'd get regular API test kits and retest. If you are using test kits, what brand are they? How old are they? They expire and give false readings. I had an ammonia kit that expired and gave a 0 reading in a newly set up QT tank. New test kit read 0.5.
Are they showing anything else other than acting weird? Look at them head on and see if you see any white coating down any of their sides. Any white blotching on fins?
Have you seen their poo? If yes, dark and solid, or white and stringy, or white and thick? Yellowish?
How are they breathing? Are any flaring their gills? Using one gill? Healthy adults should breathe approx. 60 breaths per minute. Juvies will breathe faster than that, though. After a good feed, they all breathe fast and heavy for awhile.
Have you added anything new at all to the tank? Have you had a finger in another tank and then put that finger in the Discus tank or used any equipment in another tank and then used it on the Discus tank?
I see you feed frozen foods. Have any of them partly defrosted and were then refrozen and fed to the fish?
Do you live in an area that uses chlorine/chloramine? Many times in the spring the amounts used by water treatment plants are increased. So the amounts in your tap water could have increased greatly and its possible not enough Prime or equivalent has been added to the water.
Do you have substrate in your tank? Accumulated stuff in substrate can cause Discus to become ill. Doesn't mean your tank is dirty, just that stuff in substrate can usually be tolerated more easily by other types of fish, not Discus though. Also, how often do you clean your filter? Same thing goes for the filter as for the substrate.
Anyway, I think that's enough questions for you for now.
