First of all, congratulations for your success with EC so far. My son started potty training around 32 months, which seems to be very close to average (girls tend to be a bit quicker), so you've made tremendous progress despite the current situation.
This sounds like a typical example of the "two steps forward, one step back" pattern in your child's development. I've heard it called a "wonder week"—that point in your infant or toddler's life when a developmental breakthrough is accompanied by misbehavior or an apparent loss of ability in some other area. The Women and Children's Health Network sums up the idea well:
Sometimes babies or young children will seem to have gone backwards in
their development. In fact, they are making a big step forward, but
this step is confusing to them, and they may behave more like a
Once I learned about this pattern, I began to recognize it over time in my son's behavior. You can find charts that claim to pinpoint the most likely ages, down to the week, for various developmental milestones and accompanying mood patterns—but every child is different, so those are most useful as an illustration of what might happen.
If your daughter is a little confused or distracted by the language and motor skills she's learning right now, the best thing you can do may be to moderate your response to her accidents and keep encouraging her in both her new areas of development and her previously acquired skills. She has not lost those skills! She's just suddenly got more things to process than she can deal with all at once and her brain is prioritizing her exciting language discovery over less-exciting poop and pee. (Can't fault her for that!)
As you talk with her about parts of her routine—eating, playing, using the potty, sleeping—you'll be naturally linking her new language skills to her specific potty routine and incorporating them into her general daily routine. Routine is extremely important to infants and toddlers, yet it's constantly being disrupted by growth and discovery. Two steps forward, one step back. (Yes, sometimes it feels like the reverse.) In short, keep at it.
More on Responding
I want to revisit the idea of moderating your reaction to accidents because that's less natural and possibly more important. Given you practice EC, you may have already heard this but it's worth repeating.
Whenever our expectations are not met or we are surprised by a change, we naturally get disappointed, frustrated, angry or anxious. We're no different from our kids in this way, except for having had a lot more time to build and practice coping skills. The thing to avoid here is contributing to your child's fear and anxiety, which can happen if you let your feelings lead you to scold or shout. You want your child to learn to communicate her feelings verbally, so model that behavior to her.
The way I personally approach this is by choosing to say I'm disappointed or I'm angry and using my face to communicate concern. I try to avoid angry gestures, grabbing, stomping around, slamming doors, shouting—things I don't want my child to learn from me. I try to avoid accusatory responses like you did something very bad and favor naming and identifying what happened and identifying the natural consequence—oh no, you had an accident, now we need to clean up.
Two weeks doesn't seem unreasonable for this sort of behavior. When my son's sleep patterns changed around the time of a developmental breakthrough, they sometimes would stay changed (i.e., waking up a lot) for a month or more. We might expect a child to have a little more control over a daytime behavior than over sleep patterns, though, so if your daughter's potty problem shows no sign of improvement over the next week I'd definitely look to escalate my response.
To do this, I'd start emphasizing consequences a little more, favoring natural consequences but also introducing imposed consequences. (This technique is characteristic of the Love and Logic curriculum.) For example, "now we have to clean up" is a natural consequence. My son is a big fan of his "big boy underpants" so an imposed consequence for us is sometimes that he can't have another pair after he has a poop accident (until after bed or naptime). This works particularly well for us because it's reinforced at his daycare, both by social pressure and a rule that two accidents in a day means you go back in diapers for that day. If you can identify a good opportunity to reinforce the same lesson in different contexts, go for it!
The point of escalation is mainly to avoid your daughter becoming comfortable with having accidents and deciding to make them part of the revised routine that her language discovery is forcing. I'd try to escalate slowly and consistently; again, to avoid contributing to your child's fear or anxiety (not productive for coping or growth). If the behavior hasn't corrected by the next time you attend a regular check-up or well baby visit with a family doctor or pediatrician, then I would bring it up at that point for some professional advice. You could potentially end up with a referral to a behavior specialist who can guide you all through some more focused program, if necessary. But that seems unlikely enough that I wouldn't make a specific appointment for it at such a young age, even if it means waiting another three months until her 18-month visit.