Egg colour and incubator question

Hi folks, I am new to chickens and have been putting the eggs in the incubator since we got our flock last Sunday. These are the eggs from my blue orpington, in order (minus one that had a crack in it when I found it). As you can see, she went from a very pale egg with no speckles, and as we progress, her eggs get darker and more speckled. Can anyone tell me why? Is it because her diet is different here?
Also, we have a Little Giant incubator. I set it for 99.5 but it is almost never at 99.5. It got a little warmer when we taped up the vent holes, but it still almost never makes it past 98.8 F. I moved it to a warmer room to see if that would help. Any ideas? Can I assume that the eggs will be duds if they are at less than 99.5 for a certain amount of time, or is there still hope for them?

Thanks

First, calibrate your thermometer to make sure it is accurate. The cheap thermometers that come with inexpensive incubators are often incorrect. Most of the incubators sold in stores have a +/- range of 4 degrees, which is really off for incubating. Apart from my Brinsea spot-check thermometer, I have one digital thermometer that turned out to be very accurate. You can Google how to calibrate using boiling water.

Little Giant incubators can be very quirky to downright unreliable. Here is a(long) thread about trying to improve your chances with one
https://www.backyardchickens.com/t/601352/little-giant-incubator-tricks

If you are adding eggs each day you are going to end up with a split hatch, which makes it very difficult as chicks are hatching when others are still developing. Incubators should remain unopened for the last several days of incubation, but less-developed eggs still need to be turned. You might consider collecting eggs for 10 days, then putting them in together. Eggs can be held at room temperature, but should be turned twice daily until the go in the bator. Learn more about hatching in this article from the Learning Center
https://www.backyardchickens.com/a/hatching-eggs-101

The color of a hen's eggs can vary a little.

Nice Avatar by the way - I had a wonderful Belgian Sheepdog for many years, the best dog I have ever had, still miss him like crazy

Thanks! I'll look through the thread. Re split hatch; Yes I planned on taking the older eggs out at 18 days and putting them into my homemade incubator so I could up the humidity as I understand they need a much higher humidity in the days before they hatch? The homemade one did work well but I found it was just too much tinkering on and off through the day and night and I didn't want to do that for 3 weeks, lol. I didn't know they could be at room temp for 10 days!

Re my Belgian; Thanks! That is my foundation *****, she passed away last month. I breed and show them.

Beautiful