Pick a small question
Instead of recording everything, ask whether a plant grows better near a particular window. That gives the journal a clear purpose.
Change one condition
Move the plant, then leave the watering and potting mix alone for a while. Too many simultaneous changes make the result hard to interpret.
Make the next decision
At the end of several weeks, compare what you expected with new leaves, stems and soil conditions. Keep the change only if the plant is actually doing well.
Keep the record small
A two-column note for date and observation is usually enough. The system should be easier than remembering every detail.