I have two daughters one look like a ex and the other look like their father, when I do the calulations my ex can't be the father.

Typically yes, for the best results. However, the father's parents have been known to be used in the father's absence, usually death of the father is involved when this happens.

What if you test the children would you be able to see if they have the same father from blood types

The problem with blood types is that people can have the same blood type. Do you know both men's blood types? You also need to know the genotype. Even then, it may not be as helpful as the DNA test. For example, if both men have the same genotype, then comparing blood types won't tell you anything.

I have two daughters one look like a ex and the other look like their father, when I do the calulations my ex can't be the father.

If you want an accurate answer, then you need to have the father tested.

Also, calculations aren't 100% accurate. There was a woman who gave birth to twin daughters that had been fathered by two different men. The only way to be sure is by DNA test.