I'll take a stab at this one.....
First off I would go to the Taylor Guitar website and watch their video on changing strings, especially about how many turns around the tuning peg before the strings get tight. I like to allow a little bit more slack than those folks, but only because I like to get at least 4 wraps around on the low E and 5-6 on the rest of them. That way when the strings tighten up the stress is not at the bend where the string passes through the post.
Then take a deep breath and tune the A string to 440Hz and the rest relative to that note. Give them all a little stretch with your thumb and then go to your tuner to get everything up to proper pitch. Keep in mind that your chromatic tuner doesn't care which
E you tune that bass string to, and you could have been working yourself up to the next higher E in the scale, which would surely snap the string even if it is not defective. If you KNOW that you were in the correct octave and the things gave up, you might have a couple strings that were not tempered properly which will lead to the same result. In that case I would wander them down to my local vendor and request replacements, or pitch a bitch to Elixer online which will likely get you a couple sets gratis in the interests of customer goodwill.
I usually use a 440A tuning fork, or my piano for that reference note (on piano, the A is below middle C) so there is less chance of being grossly out of pitch.
Bad strings aren't unheard of, and I even had a few G strings that were not tough enough myself.... all were gladly replaced by my local dealer for free, and the defectives sent back to the factory for testing. Also check the post holes for sharp edges or burrs which can be dressed with a small Swiss Pattern File, a good magnifier will help visually check for sharp edges... they might be sharp on one side and not on the other if they weren't well de-burred after drilling in manufacture.
Take Care, & Good Luck;
Doug