Quite a bit of air is leaking out of the air handler just below the red square plugs on either side. I think these are the condensate drain plugs? Both sides are leaking quite a bit of air noticeable when the AC is running.
How am I supposed to fix this? The air coming out isn’t very cold so it seems to be leaking prior to hitting the coils. I’m wondering if this could be contributing to excess humidity?
The leaks are causing air to escape instead of going through the coils which would lower the humidity so yes, there is an excess of humidity. Probably not much. There's usually weather stripping or a rubber gasket around the condensate ports that prevent air escaping. You could check by removing that front panel and repositioning any material meant to restrict air flow. You could also put a bead of sealant around the openings if you don't want to remove the panel. Turn off the unit for a hour to let the sealant harden.
Why is it all of sudden leaking ?
Aside of the obvious leaking seals on the cover which you can remedy the cause could be something else.
is the air flow in the vents somehow restricted ? When was it last time you clean them ?
as for cooling, when was it last time you washed the coil, you can find the special cleaner in hardware stores
