Hello. These are photos of my croton It is a year or two old ( don’t remember exactly) I foolishly took it upstairs this winter, as well as my umbrella tree and there was enormous leaf drop (The latter died.) I put it back where it used to be several weeks ago and it has been doing much better, lots of new leaves popping out. But then yesterday I noticed that a leaf had somewhat transparent spots And today it is much worse! and perhaps on other leaves as well?

is it a fungus? Should I cut the affected leaves off? Is there a cure?

In typically water from the bottom and only about Every 7-10 days (I think.) I usually check the pot weight before doing so

Thank you in advance for you help and advice!

The leaf yesterday

The leaf today! 😱

Another leaf that appears to be starting to have same issue in center of the leaf.

Another leaf that is showing dried edging. Same problem? Or inconsistant watering?

Southern window where it is positioned. Picture taken around 6/630 in the evening.