I don't have experience breeding axolotls but it would be good to check water quality as a first step. Is your tank cycled? Have you checked the parameters for ammonia, nitrite, nitrate, PH and temperature?
Not related to your question but I notice in the photos you have the little glass/plastic stones. These are pretty but unfortunately are hazardous to have in an axolotl tank. They pose a risk of the axolotl swallowing them and becoming impacted as they are not able to pass the stone. This can be fatal. I would recommend removing them.
I don't know of anything you can really do besides making sure the condition are correct so checking water quality is a good first step. Others here may have some further advice.
Also, how old are your axolotls?