I had a pair of easterns purchased from the "San Juan Snakeman" back in the 1990's and both grew to be runts. As adults, they were thick as a typical adult indigo, but only maybe 3' in length. Friend of mine many years ago had a runt Texas indigo. I believe runts crop up in indigos at a higher rate than other colubrids. I wonder if it has to do with a more limited available gene pool of captive breeders, than say cornsnakes or kingsnakes. I do not think the cause was environmental; mine ate anything and everything, they just never put on length, only girth!