deposit back

[Nichola King]

I was given a 60 day notice to move out of my rental home (be out by by Aug 31), as the owners were soming back from China and moving back in . I started moving my things over in to my new home 10 days before that date, 7 days before the lease was up the owner turned up out of the blue and asked to look around, I let him in and he asked for a spare key so he could organize measurements for new carpets etc.
5 days before moving out, he shows up at the house and told me that he had moved a new mattress into one of the bedrooms, I said nothing other than I haven't been upstairs. He then asked if I could be at the house in the at 8.30 in the morning (3 days before end of lease) so i could let the delivery guys in to deliver more mattresses. I said no, but he asked my husband the night before and my husband did.
Later that evening we had the walk through with him, sure enough the as soon as he turned up he had his kids and a car full of suitcases etc......and carried them into the house. My husband said "are you moving in" his reply was yes...the walk through was fine except some dead grass at the back which we had already offered to replace. As he had already told us he wasn't moving in until Sep 5 (not the Aug 29th )...we had agreed for him to get some quotes as the work would be best off done whilst he was there as to water it, but to not go ahead with anything until we agreed on the price. Like I said, he turned up with his things and moved in early without asking....but hey we went with the flow, cos we wanted our deposit back.
Now this is where I'm angry, Yesterday (sept 22) 22 days after the lease expired (or 24 days after he basically moved in and we gave him the keys and confirmed in a text) his agent tells us via email that they have an estimate and we owe more than the deposit to do the grass (deposit is $4600) ...there was no supporting itemized estimate or even a figure..just a a quick message. My husband spoke to the agent, and was told that was for the whole yard around the house (1000 sq ft) we have evidence of photos from moving in that the grass was dead at the front ..we only have to sod about 400 sq ft - but $4800 ?? We told the owner that we didn't damage the grass at the front...even google earth shows it dead in 2005..lol
Anyway sent an email, I offered $600 for damages and that I want the rest back by California law within 7 days or I will take them to court for the full amount. As they have taken over 21 days without any correspondence or a reason for the delay. I will be sending a letter saying the same thing in the morning of course.
Do you think I have every right here asking for most of it back? I feel like I could just say give me back the whole amount, but I want to come across as being reasonable if it ends up at small claims. I feel like they are robbing me.
2 years, Over 80k paid in rent..left the house spotless and was accommodating with the owner..even left him my ladders to borrow. What a cheek. Any advice would be great.