Are they oozing, or is it just 'on the surface' of the leaf, which I suspect? Most likely answer is that there are aphids of one sort or another, probably scale insect (look for small cream coloured discs on the midrib on the underside of the leaf). They will be exuding honeydew, which is sticky. Small infestations can be wiped off carefully. There are sprays, but confirm the problem first. If need be, come back with an update. Worthy