Yes your Nitrates are unbelievably high, 50% now and another later tonight or in the morning.
I don't think you did the ammonia one right, there should be two bottles. Add 8 drops from each bottle, shake and then wait 5 mins.
Nitrate you add 10 from the first bottle. Shake the second bottle for 30 seconds and then add 10 drops. Then shake the tube for a minute and wait 5 more mins.
old tank...I wonder if the ph is super low as well.
Have you vacuumed your gravel bed lately?
Looks right, my guess is the high nitrates are getting to him. Ideally you want nitrates under 20 but more realistically with cichlids if your under 40 your good.
I still say I'm right =>