Another question on my Betta Fish

Question
My mom brought Betta Fish's for my brother, sister, and myself.  They are in seperate tanks, unable to see one another.  We've tried to feed them their pellets(HBH BETTA BITES) but they don't eat any. They'll sometimes put one in their mouth then spit it out.  Is their something wrong?  How long should the pellets stay in the tank before I have to take them out?

Answer
Well if they don't eat those try frozen bloodworms and try to alternate between the bloodworms and the pellets. If they still don't eat the pellets try "Omega One Betta buffet" those are flakes so they can consume them easier. The food should only stay in the tank for 5 minutes at the max.so the food doesn't darken the water.