get three glasses of tank water, place one on a window sill, place the other two somewhere stable but add a teaspoon of sugar to one and stir it, after 24hrs check the glasses, if the one on the window sill is more cloudy/green then there are nutrients in the water causing algae bloom, if the one that had sugar added is more cloudy then it is bacteria bloom in the water, if the third glass (or any of the other two) seem less cloudy but there is dust at the bottom of the glass then the cloudiness is caused by minerals (limescale) dropping out of the water column.
for algae use plants water changes to remove nutrients, nitrates and phosphates.
for bacteria bloom increase biological filter media.
for limescale ensure that enough mechanical filtration is used (mechanical filtration is the fine/medium/coarse foam stage of the filter), if needs be add filter floss.
provided there is adequate water oxygenation cloudy water won't effect your axolotl (in the wild they stay in the muddy silt areas)