Water! Water!
Ok, the KH is good so the pH had not crashed.
You have massive nitrite readings, so more water changes are in order. The nitrates are too high also, so start doing larger water changes. Daily water changes are not too much, 50% at at ime is OK too, just be sure to match temps and dechlor as required. Get the nitrites to 1.0 or less and the nitrates to 20 or less.
Catfish, yes, after the cycle is complete otherwise they will lose their whiskers. Rainbow fish, probably not, the tank is too small. African frog, I dunno, does it eat fish? You cna have something near 10 inces of fish in this tank. You have more than 5 inches already, and the atfish are better in large groups.
Really a 10 gallon is nice to do with one species, 6 or 8 fish, and one group of catfish or other bottom dweller. How about just white clouds and catfish? 8 white clouds and 5 very small catfish would work. You just can't fit many fish into a 10 gallon while respectng most fishes need for a group of 6 or more!!
Most important, do not add anything until the nitrites are zero and nitrates are low with increased water changes.