
Of course the guinea pig noises are normal, but they should be feeding most of the time when not asleep.
I find once the milk is really flowing well while they suckle they hum like zebra finches.
How much have they gained in weight. Mine had gained 7 - 9 ounces in the first week and today at two weeks had gained in total between a pound and 1lb 6oz since birth. I would expect the pups to have gained by a week old 7 ounces approximately, and in the second week to be gaining an ounce and a half a day (say 10 ounces that second week).
It could be as the bitch was rather stressed (sitting on the pups) that her milk is slow in letting down, so she needs to be able to relax.
How are they in the box, spreading out or all on top of each other, this will tell you if their too cold or too hot. If warm enough they will snuggle up in two's or threes but not lie in a heap, if too warm they will scatter away from each other.