Help!

I’ve had my fiddle leaf fig since August, so about 3 months. She was potted by the nursery in a large pot with no drainage but with rocks in the bottom. When I first got her, she was healthy and happy for about a month, then I started noticing browning on her leaves. I ordered a moisture meter on Amazon, and it told me that the soil in the root ball was wet, so I assumed the browning was due to root rot. I pulled out the root ball and trimmed any spots that looked dead, then repotted her with new soil in a pot with a drainage hole. This was about 3 weeks ago. Since then, the browning has continued and even worsened. I’ve been giving her about 2 cups of water every week. She sits by the window in indirect light. What can I do to stop the browning?