Issue with Iphone 6 erasing text in text fields in apps

I have this issue with 2 apps so far. Those being Starbucks and Fitbit. I haven't been able to find a fix for this but whenever I enter text into a text field (for example the username or password entry field) and i go to select the next field, it automatically erases what I wrote in the first field. So if I was trying to log into the Fitbit app, I would put in my email address for the username and then when I go to put my password in, my email gets erased. I took my sister's iPhone 6, both of them running iOS 8.1.1 and she is not having any issues with this. Has anyone else come across this problem? I want to try and see what other apps this is an issue with but honestly am scared of signing out of them in case I cant get back in. Thanks!