78 yrs old with multiple lithotipsys. Is now experiencing a yellow vaginal disharge can this be related to kidney stones?

Doubt it. Not likely, but if you received antibiotics recently then a secondary yeast infection is a good possibility.
No. No. Depending on whether or not you were treated with antibiotics you could developed vaginal infection either bacterial or trichomonas since you said is yellow.
No. Kidney stones are not related to vaginal discharge. They may cause a urinary tract infection but there should still not be an associated vaginal discharge.