What size prong collar are you using? There's small, medium, and large. I have to use a medium on Tala even though she's only around 30 pounds. She doesn't respond to the small one. The whole idea is that the prong collar makes the dog self-correct so they're not choking themselves. But, if the collar is not working for your dogs, you'll do more damage by using it. You could try the sporn harness, but I found it less effective than the prong collar. You can always return the harness if it doesn't work too.
BTW, the rubber caps to make a difference. The collars are more effective without them.
If the sporn harness works, then that's great. I wasn't successful with them, though.