My 19 week old Isa brown layed a strange egg. She has been laying for approx one week. She was in the nesting box for some time this morning and did not lay. She was not as active as usual tonight and then layed this egg in the yard. It is fully formed on the inside. Soft on the outside and has a "gooey" substance on the outaide;you can see it somewhat in the picture. Please let me know what I should do. They have free choice oyster shells.