OP- when you say the soil is "old", what do you mean? Has it been previously used?
If so, what was the previous cultivar?

Do you, or does anybody else in the dwelling, smoke tobacco?

Would it be possible to get a shot of the underside of an effected leaf?

Have you had any whitefly or aphid issues?

How quickly is this progressing? Days, weeks,...?

Are there any cankers where petitole meets meristem?

How old is this mom? When was the last time she was trimmed? Did you take cuts of any of your other moms at the same time?

I would quarantine that plant.