Ford: coolant leak on 93 1.9.wierd?

hello again. well cars been running great but,
there is coolant leaking just a few drops and its at the bottom of the
transaxle.
i pulled of the inspection plate and can tell its been leaking awhile.
so does the freeze plug between the engine and tranny go bad ie leak? ive
always had coolant in it no rust.
or could the head gasket be leaking coolant. or intake manifold gasket?
i have examined all the external areas and there is nothing leaking outside.
the sensors and heater hose anrent leaking. pulled the batt to check the
rear of block nothing.
flex plate has residue from coolant on it.
HELP before i start tearing this puppy apart.
thanks
Matt