Hoa Threatening Fines Over My "non Grass" Lawn Even Though I Used Their Approved Plant List

Location: Phoenix, AZ

So about 18 months ago I redid my front lawn because keeping regular grass alive here was costing me like $200 extra in water bills every month and I wanted to put some of that saved money toward other stuff. I checked the HOA guidelines and they had this whole approved plant list for drought tolerant landscaping. I picked buffalo grass mixed with some native ground cover that was literally on page 3 of their list, got quotes from landscapers, did the whole thing properly.

Fast forward to last month and we got a new HOA board. They sent me a violation notice saying my yard doesn't meet community standards because I don't have a "traditional turf grass lawn" and I need to replace it within 60 days or face $100/day fines. I emailed them back with a copy of the approved plant list from 2023 showing exactly what I planted, and they responded saying that list is "outdated guidance" and the new board has decided only Kentucky bluegrass or Bermuda grass counts as acceptable lawn coverage.

The thing is, my yard looks fine? Its green, its maintained, no weeds or anything. My neighbors grass is literally dead and brown right now because of water restrictions and somehow thats ok but mine isnt. Also I spent about $4k on this installation.

Do they have the right to just change the rules like this and force me to rip everything out? I followed their guidelines when I did this. Is this some kind of selective enforcement thing? Should I just respond to them in writing again or do I need to get a lawyer involved already

Thanks for any advice