Hi all. Bought this house in March. The pool and water features were built in 2006. I’ve noticed that it’s been leaking a lot. Like, I’m adding 120lb of salt a month and my water bill is sky high due to autofill. I had two reputable pool leak detection companies pressure test the piping and everything and they concluded that it must be leaking from the waterfall. I’ve noticed some grout missing between many of the rocks. What is a suitable product to patch the missing grout? I called a few pool companies and they are just too busy to do repairs. Thank you for any suggestions 