Are you using PVA? You don't need pva for all those windows. Even the ones at the very top. PVA can create those holes. If those aren't pva holes then they might be due to speed changes.
To fix PVA holes, block support where those windows are. The tops of the windows have a "bridge" and your printer can bridge pretty well. Especially such a short distance. A good example of a bridge would be the top of a door frame. More info here - look at the first two bridge photos here:
To fix holes due to speed changes - get rid of speed changes. Change all your printing speeds to 30mm/sec and the quality of your print will go up drastically. Leave the bottom layer speed at 20mm/sec. Leave the travel speed at 150mm/sec (or faster). Anytime you have a speed change you get overextrusion or underextrusion because it takes a while for the pressure in the nozzle to stabilize.
Also the base and the tower were printed separately at so the cantilever was not including in the print.
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