Yoyos get like 5" long and are super active. I recommend a 4' tank for them. If you can lay hands on Botia striata (Zebra Loaches), they stay smaller (around 3.5") and Yasuhikotakia sidthimunki (Dwarf Chain Loach, Monkey Loach) stay under 2.5" and move like no other fish. I keep them in a tank with Red Eye Tetras (though it's a 50 gallon that also has a shoal of Botia kubotai, an SAE, and a Bristlenosed pleco in there.)
So my recommendation is to switch out your 3 Yoyos for 5 Striatas or 6 Sidthimunkis.
If you aren't going to do that, then add another 3 to 5 zebra danios or ditch the danios entirely and add another 3 or 4 red eye tetras.
Remember to Quarantine! Loaches HATE ich.