Hi Steve.
pH will not affect drying time unless you manage to set up an exothermic reaction, the Texatherm system is supposed to do this.
Anyway I digress two factors are adding to the drying time, the general high humidity and cool temps and the added protector.
Protectors contain water and a film former, which will slow drying as the film envelopes the carpet fibres.
Tell them to put the heating on and ventaillate well, should be no problem.
Cheers
Doug