I have a gunite pool and in several places where the tile meets what I guess is the plaster , some chunks have come off and I can see more want to if given a love tap ;-). Noting really below that tile line and only in a few places , so hoping I can repair and keep the situation from worsening. What product can I use to repair this ? Is there a way to at least try to match color ? Hoping to get this fixed before closing. Thanks in advance !!