Ocellaris clownfish's middle stripe fading?

[OcellarisClowns]

After today's weekly 10% water change and their mid-week diet of Frozen Mysis Shrimp, my female of the pair has started to fade in the middle stripe after the lights went out.

I believe she's pregnant as they are starting to pre-spawn cleanup or whatever but I wanted to find out for myself so I did some research and came up with it being cause by an anemone, which I don't have, or a disease... What do I do?

Finished testing the chemicals with a test strip twice, 100% perfect.
Checked the salinity, and it's right inbetween 1.023 - 1.024, which is good.

 

[TheTodd]

I don't have much experience with clowns, so I can not advise there, but I would consider getting a test kit, not strips. They are notoriously inaccurate and don't give the same feeling of being a scientist. . The first matters...the second not so much.