Technically, you needed to notify the County when the first property was no longer your principal residence. According to this Q&A Orange County website: http://www.ocgov.com/assessor/faq.asp#HE
"If you do not own and occupy your home as your principal place of residence, you must cancel your Homeowner's Exemption. You can cancel the exemption by writing to our office, or using the termination form included with your property tax bill. Please let us know the date you moved, and provide your new mailing address."
Also, while not the same County, you will note that the Homeowners Exemption removal form of this other CA County indicates penalties may be levied via California Revenue and Taxation Code Section 531.6
Given that the exemption only covers $7000 of value, and that penalties can accrue, you may want to remove the exemption sooner than later.