A couple of things for you to consider which may help narrow things down.
If the "bits" attached to the glass are tiny white moving worm type creatures then they'll be planaria which are just a harmless detritus worm. They indicate that too much food is being fed, they thrive when there is an abundance of uneaten food. Cut down on feeding and they'll disappear as fast as they arrived.
However, the floating white flaky bits don't look like worms at all. Sometimes when you turn your pumps back on after a water change the thrust of water rushing through the plumbing can dislodge bio film layers which have built up over time. They look unsightly for a while but will clear up. Some fish will even eat the bits!
The last one, and one which I've experienced on a couple of occasions, is that the bits could be particles of slime coat off your fish. Maybe the water board have been messing with the water supply, or maybe you added too little conditioner, or worse, forget altogether. The stress of this new water after a water change will cause your fish to shed slime to protect themselves.
Hope this helps.