Under Section 60D, a public holiday falling on a rest day, the following day will be the public holiday as below:
Provided that if any of the public holidays referred to in paragraphs (a) and (b) falls on a rest day the working day following immediately the rest day shall be a paid holiday in substitution of that public holiday.; ..."
But it does not say what will happen if the replaced public holidays again falls on another public holiday. So, as far as the EA is concerned, it is not clear whether the following day, in your case 21 July should be another replaced holiday. If I am not mistaken, government departments in NS, 21 July will also be closed. As such, you better contact the Labour Department in NS for an official opinion.
Do give your feedback here when get an answer from Labour Department as guidance for all of us.