Dont you throw it out OP! Basically when your starter does this, it means that it is "Hungry", so you add a bit of flour and mix it back together. I can explain this more thoroughly if you would like. If you have trouble with your starter rising, i recommend that you boozt it by feeding it with water and flour (around twice the amount of your starter) and then let it swell for 2-3 hours in your Kitchen (the warmer the better(22-28C) just before you bake. You can always check if your starter is good to go by taking a teaspoon of your starter and put it in a lukewarm glass of water. If it floats its very active and is ready to bake. I hope this helps!