Question for toilet trained cat owners

Hi guys im brand new to this site
Im a brand new mother of 2 himmy boys that were given to me by a friend. Theyre 4 yrs old and have been well trained since they were young to use the toilet.
They were very good with using the toilet for about 2 weeks but last night when my husband and i got home one of them had peed on the floor. We looked in the toilet and there was a lot of poop. Probably two cats worth of feces. I have another bathrom but for some reason they used it in the beginning but they both stopped and just use that one toilet.
My question is, did they pee on the kitchen floor because the toilet was so full or is there some kind of behavioral message behind what happened
Sorry if this sounds like a dumv question but i need some answers to put me at ease. If theres something wrong that im doing can someone help me out?
Thank you

Actually if anyone has an answer to how i can get my cats to start using the other toilet that would be great help. I dont get it
The toilet is wiped clean but they just want to use that one toilet

If they're like my cats, they'll use one till they get bored with it then use the other...

If I were trying to get them interested in something, I would "season it" with catnip.