It's hard to tell from the pic's , but looks like a pre-flower (a little white hair) on your second pic. These show up on females around 8 weeks of age.
Might need a magnifing glass to see them.
Wish I'd checked this thread before I bought my Hanna Checker pH meter.
I can dip it in the same solution 3 times in a row and get 3 different readings.
Looks like the ph600 for me.
Thanks for the reviews.