There are numerous ways that buyers can back out of a purchase duringi the 17 day contingency period. In the current market, it is just as important for the PROPERTY to appraise as for the buyers to qualify. GIven the shifting market as long as the buyer's qualifications don't change (such as losing their job), then the appraisal and inspections need to pass also. Lenders are being very careful on homes that they loan, so a positive wood destroying pest inspection report and physical inspection report will help. I am guessing in Valencia your home is newer, so that should not be a problem. In some older homes, for exanple, if the roof is nearing the end of it's life, the lender might require that prior to the close of escrow the roof be replaced.
Going back to what I had mentioned at the beginning, buyers have any ways to back out of a purchase. Your Realtor's job is to monitor the buyer's progress and make sure that they are performing as agreed. You say you have two offers, is one a backup? Then it is even more important for the Realtor to monitor the buyer's progress and be aware of any issues in the process. You Realtor will no doubt be in touch with the buyer's lender directly to check on their progress, as well as checking on the appraisals and facilitating the other inspections. The main thing to know is that every time a new report is given to the buyers, a new three day recission period kicks in, meaning they have three days to cancel.
That means that you and your Realtor should do everything you can to have all the disclosures prepared as soon as possible for the buyers to review and acknowledge.
Good luck, hope it goes well for you