I'm guessing with levels risking that quickly that there are quite a few fish in there? Sorry, I don't know your tank/post history beyond this thread but will have a scan over it later. Don't feed the fish for now, since more food in = more waste out, and fish can go for weeks without food, since they take their body temperature from the water and don't need food to keep their body temp up like us mammals do. So, fasting them for a few days won't harm them, and will give the bacteria time to catch up.
You've shown that you have both types of bacteria, so you're closer to being there than you think! I know all the water changes gets old after a while, but it really is temporary, you'll get through it!
Once things settle in and the tank gets established, once per week changes are usually enough, depending on tank size and stocking of course. Poor plant does look a bit battered! But will hopefully perk up in the tank. Some of those lower leaves do look a bit like water wisteria, so it might be, but the plant being a bit battered makes it tough to tell. It should perk up now it's in the tank, and plants help to process ammonia, so this one and the water lettuce should help too, gotta be patient.
If the suspected water wisteria doesn't perk up though and starts to look as though it might be dying, send a photo for us to check, since dying plant matter can also release ammonia. Unlikely to be a problem, and doesn't mean the plant can't be saved so don't be too quick to remove it, let us check it first, since sometimes trimming and removing the dead/dying parts is enough and they can be removed, then the rest of the plant flourishes. Not likely to be a problem, but wanted to let you know, just in case!
