Yep, new tanks, transfer shock and especially novice mistakes can severely effect plants. If after 2-3mo your still having problems with simple plants like this then we can start looking at user error, source water problems. New tanks are unstable to begin with, especially if you don’t have a basic knowledge of water quality/chemistry and interactions that can happen.
Seems you overdosed ammonia, lesson learned. Small gradual changes are best coarse in keeping aquariums. Rapid shifts in water chemistry very seldom works out way you want.
Learn your source water for water changes. Put some of it in a bucket, let it set for 24hrs to absorb gases (mainly CO2) from atmosphere, measure PH, KH, GH, Nitrate, Phosphate. That’s the water you have to work with. Only change from that in tank your going to get is from decomposition of leaves of plants rotting away, decomposition of excess food or fish/fauna poop. Organic acids.
Look beyond the “it’s just a big fish bowl full of water” that most beginners assume. It’s actually a complex interaction of gases that are absorbed into water, mineral content levels and organic compound bio-load, a ecosystem, if one part of that ecosystem crashes many more failures are going to follow. Balance when you obtain it and looking at your thriving tank is what makes you smile in this hobby.
Routine and consistency managing that routine is where you’ll find balance/equilibrium in your tank. Not seeing a slight problem and bombing your tank with adsurd changes trying to correct it is where you succeed in aquarium keeping.