The stigma against double texting is an insecure schoolgirl affectation. Don’t worry about it.
Personally I detest chain-texts (a whole bunch of short messages in quick succession, like 8-10 or so) because a) I get the impression the writer didn’t want to bother organizing his thoughts before communicating, and expects me to do it for him and b) it makes my phone vibrate/beep a lot and it’s just distracting. But that is not what’s going on here. It’s just two texts with complete sentences.
TLDR: you’re fine, texting etiquette-wise. Double texting is not really a thing.