Advice for depressed partner

Hi all, I am a partner of a someone who is going through a depressive episode. I just want some tips or advice on how to support them/what not to do since my partner isn't communicating all that well to me about their needs.

I've been with my partner for more than 6 years, and throughout our entire relationship it's been amazing, we loved and adored eachother - always hung out and spoke with eachother every free moment of the day. Suddenly they started feeling sad in the beginning of winter (which makes me think this is SAD as their sleep is getting worse and they're not getting much sunlight) and it's been downhill since then. We no longer see eachother as often, talk as often, and when they speak to me it's quite flat. We have never had this happen before in our relationship, but they said that they used to feel like this before us.

I just want to know what those who go through depressive episodes would appreciate as support? I always let them know I am here for them, that they're a great partner/friend/person, I tell them they don't need to reply as fast but I am thinking of them. However, there are times where I get really anxious (I have an anxious attachment) and I ask them if we're still okay, if they still love me etc - is this making it worse? Can someone explain why? I just need clarity, thank you all! :)