Cannot pick up clear temp differences

I was looking for an app that could help me match lighting sources. When replacing burned out sources, its important to match the color temp of the replacement with other existing sources. So I downloaded this app in hopes that it would be a handy tool. Not so much.
I tested the app with two banks of fluorescent tubes, each was clearly either daylight or a much warmer color. If I could upload a photo, you would easily see the difference. Yet this app rated them at essentially the same degrees Kelvin, 5150 (actual: 7 degrees different).
Maybe the eye and camera is very sensitive to color shifts and consequently its too much to ask of an inexpensive app to resolve the difference. But using this app to chose replacement bulbs in a home or office would give unreliable results in matching sources.

RAPrice about Lux Meter - light measurement tool for measuring lumens, foot candles, lx and light temperature, v1.3