It's pretty natural to see this kind of pattern. You were trending early, making your work more visible and you got used to 2 per day. This isn't a typical rate of new subs for a series with a small number of subs; I'd expect more like... picking up somewhere around 5 a week mostly clustered around update day at that size.
Exactly how trending works isn't clear, but from my observations, very new series that are doing quite well seem to have an advantage, and usually it contains just very big and very small works and not a lot in-between (for example, when my comic was on staff pick, and my subscribers increased by 80% in a week, going from 275 to 500 and I was near the top of my genre in the "Popular" rankings, I didn't trend once) so I think it's good to understand that you have to pace yourself. This might be the typical pace of things for a while now. Keep updating, keep promoting and you should get a steady trickle of subs that increases over time.
It could be worse. A couple of weeks after I was staff pick, I had a run of weeks where my new subs didn't outpace people unsubbing and had to deal with my subs going downwards! It seems to have steadied now, but yeah... sometimes subs plateau or even decrease. The best thing is not to pay attention to the minute numbers too much and instead to focus on making something good and letting people know about it.