That a pretty small grain bill for a large cooler. I'm not surprised with the temp loss. But you should not have much of an issue with it.
It's possible the cooler didn't fully heat up.
I heat all my mash water to 170* and add the to the cooler. Allowing the temp to drop to 160. Then add the grain. Stir till the temp drops to 150*.
You added 3.5 gallons for the 2nd runnings but received 3.75. Looks like you made up for the low 1st runnings?
Is your lower volume the preboil or post boil? If you had what you wanted preboil, then you had better boil off rate than normal or boiled longer than normal. You just need a little more water to account for this.