I would do a continuity check between the leads of the capacitors and wherever they go on the circuit board, that would help rule out a bad solder joint. The solder does look suspect, a good joint will usually be shiny and a bad / cold joint will be dull. I would also use some flux cleaner of isopropyl alcohol and cotton swabs to clean up the PCB around the solder joints, as there's a lot of gunk from the solder job which can hide issues below.
It also looks like the base of the new C551 has some damage, but it could be an artifact of the photo. Where did you source these capacitors? You generally want to avoid cheap no-name brand caps when recapping sensitive electronics. I try to source all my replacement parts from Digikey or Mouser even though it's usually a little pricier.