I do not understand much about washing machines, but it does not seem logical that tightening a belt would cause a leak to cease.
1) I agree with you.
2) Your washer does not have a belt.
A plastic tray under in which the washer sits has water in it
Probably a leak catcher, many "upstairs" washers use a similier device...
Pan, for under washers Fits most standard, large, and extra-large washers. Optional floor drain connection included
In addition, there appears to be a drain pipe away from the plastic tray through the floor - could the leak be coming from there (the washer is on the top floor and leak was spotted as water dripping onto lower floor).
The drain part of the pan can leak or the pan could be cracked....but, the washer is likely leaking first onto/into the pan.
Direct drive style washer ( no belt ) built by Whirlpool for Sears.
WATER LEAKS FROM MACHINE: -Some- common trouble makers.
~Drain Hose Cracked
~Stand Pipe For Washer Drain Backing up _ Fill tub to highest setting and run through spin cycle and see if the drain backs up.- If yes, call the plumber.
~Tub seal, support seals, basket drive seals leaking.
~Hole in plastic outer tub.
~Fill valve leaking
Take apart helps to have a peek...
Drain pump for belt-less direct-drive washer, one large port, one small port
for Model # 110.22902100