As you guessed, 25 psi is likely way too low for a 187QB.
Best practice is to fully load the trailer for travel and take it to a CAT scale. Get weight of trailer for less than $20.
Divide CAT weight by 4 (4 tires).
Federal law requires a tire spec chart be attached to the trailer. Usually it is on the driver's side near the front. Older trailers may have the spec stamped into the tongue frame on the driver's side.
If not, use a tire pressure chart or calculator to determine optimum tire pressure.
I run mine at 50 psi because weight of trailer is near maximum tire capacity.
Tires - Rear Tire (Full Spec) - ST205/75 R14C
https://www.rvusa.com/rv-guide/2012-...-specs-tr10752
https://www.etrailer.com/question-649692.html