Looking for a betta safe fertilizer

I have a new 2.5 g planted Betta tank and the plants are starting to look a little yellow/dull.

To be fair, I did put them through a bit of an ordeal during the last lap of a fishless cycle. They were in the tank for a little over a week with the temp up to 83* and kept mostly in the dark.

The plants that I'm trying to revive are- 1 anubias, small bunch of Java *moss and a small bunch of anarcharis. The cycle was completed and the fish was added only a week ago. The temp is anywhere from 79* to 81* and the light in the tank is LED.

Wondering if if I need a fertilizer or a different selection of plants (?)

I'm already a paranoid fish-mom and am scared to add anything that could kill my Betta. He is however, quite fond of the plants in his tank and I don't want to deprive him of them. Any advice is welcomed! Thanks

 

What kind of light do you have?

Are the Anubias or Java fern planted?

 

It's a little LED light in the lid of the aquarium.

The Java moss (I have to edit my post from before where I put "fern" by accident) is just floating and sorta pushed through the handle of the espresso mug. The anubias I made a holder out of small rocks held together with silicone (added picture because it's hard to describe.)
I made sure the rhizome was not covered or stuffed inside and it gets plenty of water flow.

 

I'm wondering if the light is too low. Most kit lights aren't very good.

 

Now that you mention it, the light is really small :/