Depending on your source of water, the water changes could be encouraging dyno growth, as your source water could be providing nutrients to the dyno.
1. are you using RO water? if not, this is likely your problem. try using RO water instead.
2. skimming, skimming should remove the nutrients that will encourage it. Make sure that youre skimming effectively. You can check this by testing for phosphates. Even tho its not the actual phosphate thats the problem, phosphate is used as an indicator for several known and unknown trace elements and can be used to gauge theyre counts.
3. what substrate are you using, if its silica base, this is also another problem, as dyno is silica based and needs it to grow. if your substrate is silica based, then you will have to wait until the silica is depleted from the surface of your substrate (it does disolve into the water, and will evenly get depleted).
Anther thing is wet/dry filters. Apparently this is a source of dyno. I'm not sure how, but apparently many reefers have reported that after they removed the bioballs (and replied purely on natural (LR, DSB) for filtration), dyno disappeared for good immediately. I'm sure there will be some literature around that may explain this.
