Please help. How to repair tile & plaster on gunite pool

Hi,

I have 3 tiles which have fallen off from the side of the pool They are all above the pool line over the skimmer entrance.

I tried to use a quick patch cement to reattach them but then I noticed that the plaster beneath them was loose and fell off as well. Now there is exposed cement where the tiles used to be.

What is the best way to go about repairing this?

Do I have to first put plaster and let it cure and then cement the tiles to the cured plaster, or do I just cement the tiles directly to the exposed cement (as my pool store told me to do). I presume the best way is to apply the plaster first since that was the original design.

Anyone have any clarification for this?

Thanks for the help!