Toilet leak while and after washing clothes.

My downstairs toilet leaks a small amount at rear of base. It seems to only leak during or around the time laundry is being done. The toilet flushes, drains completely, and fills beautifully, that is not the issue. It simply leaks a small amount (a shot glass) at the back of the base. I cannot tell for sure that the water is coming from under the base but it sure seems like it is. It might, not likely but possibly, be coming from the back of the tank/bowl connection. I have watched this toilet for three weeks now and cannot detect any leakage before the wash is done, only during and soon after it is done. All info I have found for wash machine/toilet issues seems to note a problem with toilet flushing/bubbling/gurgling/overflowing. This one flushes perfectly. Just leaks when the wash machine, on the same ground floor about 12 feet away (hall bathroom to kitchen area where laundry is located) is used. This is in a 2-story condo built in the 80s. Can anyone help me with this? I am not sure what larger issue may be causing this and am about to simply change the floor donut and the tank seal, then recaulk, to see if issue goes away.
Thank you for your time.
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