loose timing belt ?

[ebpda9]

i noticed that my car lately had a major loss of power, and i was in dire need of a valve lash adjustament, so i just did it yesterday. Oneweird thing i noticed was that the timing belt was kinda loose( just not enough to slip over teeth). the belt looks like it was changed since it does not have any cracks or any signes of wear on it. i know it can be tightened but does anyone know how to do it ?

P.S. Does anyone know of an online shop that sells metric feeler gauges ? i couldn't find one locally even at the autoparts stores or speciality stores.