The pictures are so blurry that nothing is clear enough to see anything precisely.  But it appears these could be aphids sucking happily on your plants, unless these all have dark thorns.  Look with a hand lens and see if you can match the shapes up to aphids .  Look online to see an aphid shape.  If it appears that these are aphids, which are insects, spray with Insecticidal Soap.  You buy this, not mix it up with products from under the sink.  Spray in the evening when the sun is not on the plants and plants are not water-stressed.

But why are you growing apple rootstock right against the foundation of the house?  You are going to have heat-stressed plants that make aphids likely and not have room for a good root system to develop.  And why are you buying rootstock instead of already-grafted apples?

Again, the camera does not focus.  It could be a cotton ball or a small cloud.  If the material is slightly sticky, sort of like cotton candy, it is very likely aphid-related.

Be aware that your rootstock in small buckets will end up being very root-bound, if they are not already.  If there is only a tangle of roots, a successful graft will not mean much.  The aphids are currently voting on "stressed apple rootstocks."