Multiple Issues

[Otter2009]

I have 20 gallon and 36 gallon planted tanks (the 36 has CO2 and the 20 does not). I've gone back and forth on using/ not using fertilizer with them but had settled on not using it a few months ago. About a month ago I noticed a lack of growth from some plants and started using Tropica Premium Nutrition in conjunction with Excel to limit algae growth.

This week, I found numerous holes in my plants' leaves (mostly on the anubias plants) and that some plants had stopped growing entirely. I did a water change and reverted to using Thrive. Today, I found my ammonia levels had spiked in both tanks and one has a lot of brown algae growing.

I'm at a loss for what is going on/ how to fix it and would love some advice.

 

[quinnmquinn]

I’d stop dosing fertilizer and see if the problems resolve themselves. I have a 36 gallon with CO2 too, it’s been set up for 2 years and I’ve never tried liquid fertilizer, just root tabs.
I’ve heard some plants get hurt by those fertilizers because they have an algaecide (no idea how to spell, algae killer) and some plants are very similar and it can cause melt. One I know of that does it is vallisneria.

 

[Otter2009]

Thanks, I stopped fertilizers and did a water change. Unfortunately, one of my fish has since died and the others are acting as if ammonia levels are high (but they're testing as 0). Some of my plants have also started losing their leaves.

Any thoughts?