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I live in a shared house with another two male roomates (both in their 20s). I (30 F) have been living here for almost 2 years, and one roomate, whom I'll call John, has been living here for about 6 months. We welcomed a 3rd roomie, whom I'll call Andy, last week, and I can't complain about him.
Nevertheless, I complain about John's bathroom habits (and should I say, cleaning habits in general). I don't tell him all the time, but the times I've complained out loud he says it's not his fault, it was like that when he got here or stays quiet. For example, he leaves the dishes in the dish rack for days and the dish rack has caught mold some times (and our tenant, whenever she comes to check out the place, washes it, or I wash it eventually). He leaves the washing machine on for hours. He doesn't think the kitchen needs to be deep cleaned.

But my main issue is the toilet. He usually leaves the bathroom without flushing the toilet. he says he does but I've find it dirty so many times it's getting on my nerves. I tried to talk to him and he said "it's not my fault, the toilet doesn't flush correctly, I'd need to flush it two times" and I said "well, then wait for it to fill in and flush it again, you need to leave the toilet clean", but he doesn't seem to care.

I started to send messages to the whatsapp group we're in (the tenant, John, myself and now Andy) and the tenant just says "you need to respect the house and your roomies and clean after yourselves", and whenever she's here, she talks to John and he says he gets it, it wasn't him or tries to blame it on another stuff, it's "never his fault". Last night it happened again, so I texted the group and he didn't even answer when it was obvious it was him. The tenant is getting tired too, and I think Andy got uncomfortable, but at this point, I can barely care, because he doesn't seem to get ashamed. WIBTA if I continue on the texting every time he leaves the toilet dirty, exposing his bad cleaning habits, until he really changes and/or gets ashamed?

FYI: I'm not thinking of moving out, this place is great for me (and I was here first). Technically, the tenant can only wait for him to "want to move out".