Age/Species confirmation?

Hello so im relatively new to snakes and i was wondering if i could have some help with age/species of my new garter. Sorry the pictures are so grainy x.x Its hard to tell but he has darker spots in 4 rows (2 rows between each stripe of yellow)

I initially thought he was a Eastern Ribbon but they dont have the face stripes running from the eye to the upper lip. Another option i considered was Eastern Garter but they dont have such bold and bright side stripes. I believe he is a Butler Garter (T butleri) but i really dont know, could someone confirm/deny this?

The other thing is i dont know his hatch date/age. I got him from a reptile shop (East Bay Vivarium) and i dont know if they even have it. Right now hes ~26-28 inches and 39 grams (weighed yesterday) Whats perplexing is he is too lightweight to be an adult (i think) so is he just a long juvie or a light subadult or something else??

I think it is a Thamnophis radix(Plains garter) but it is very hard to tell from those photos, looks a bit skinny as well. A photo of the vent and tail will make it easy to determine the sex of the animal. As for the length/weight I think one of your measurements might be slightly off, 39g seems really light for a 26" long snake. This animal is also an adult, 3 years old+ if a male.

Agree with it being radix, maybe a male. Its probably a wild caught. A female at this time of year would be huge in the back end with babies