Sometimes Kribs can be a little finnicky when it comes to the right time to spawn.
First of all, the water must be clean with plenty of oxygen. I'm not saying you need to do water changes everyday, but your water should be clean. Do not worry about water parameters such as pH, KH, or GH. If that part is taken care of, then diet is next. Obvioulsy, you are taking care of that part as well. I would cut down on your feedings to 1-2 times per day. Three feedings per day can introduce excess phophorous and nitrogen, thus reducing water quality. I feed my Kribs TetraMin Pro and Hikari frozen bloodworms. Sometimes they get brine shrimp.
The Kribs must court each other--you will know when they do so by their flaring fins and maroon bellies. Only then will know they will eventually spawn. The female is the one who chooses the spawning site, not the male, and you will know she is ready to create one when her belly is sagging a bit. The more cover it has, the better (this may be the main issue for you). Kribs are very defensive parents, and will aggressively defend their territory, especially after the female has layed eggs.
I have noticed that Kribs spawn much more readily when the number of tankmates are kept to a minimum. So if you have excess fish, get rid of them. I would choose the guppies if I were you, as most guppies do not have a defined swimming area, as opposed to your danios.
Other than that, you just have to wait. It took forever for my pair to spawn for the first time. They are now on their fourth spawn, and show no signs of giving up!
