Not the fastest growth by any means and looks a bit droopy.
Could be any number of factors that can result in slower growth rates.
Cold nights will definitely slow it down. Anything under 68F impacts biological process at least a little bit and more so the further it drops. This is why you get fall colors in the leaves outside, too.
The soil is hard to see but looks like it's got very little perlite or similar. If it's a soil/sphagnum peat moss base with high water capacity, you want about a 1:1 ratio with perlite or vermiculite. This provides the optimal gas:water mixture in substrate as well as a fluffier substrate that allows for more optimal root growth.
soil nutes.. the type that require microbes to break things down to be plant available generally result in slower growth rates. switching to a soilless method would have immediate and noticeable improvements to growth rate with little to no learning curve...
watering habits.. sounds like you are choosing what to do whimsically or what 'feels' right. Don't do that. The plant dictates proper amount of time between and when to re-irrigate.
1) water entirety (10% runoff if soilless, minimal runoff for soil to ensure fully saturated)
2) wait for approriate dryback -- 1" deep dries in a high water capacity soil is a good trigger. Can also use loss of weight from pot.
the dry back should trigger re-irrigation and nothing else. Something like coco you re-irrigate a bit sooner because it holds about 2/3rds the water per volume than a typical soil. 1" deep drying in coco might cause wilting... avoid wilt, obviously.
as long as the spacing between nodes isn't unusually tight, it's probably not stunted by too much light.
if it's been consitently cold, that's probably why... but there are figuratively 100s of possibilities.