White spots on bottom of stem

Nothing to worry about, if you topped up your grow medium you would find roots will grow from them spots.

root nodes. to wet to long, need better wet and dry cycle in the medium should help curve the algee growth on the perlite.

It is normal. If that portion of stem was to somehow become buried, this is where new roots would sprout from. Google "adventitious roots" if you want to know more.........but ignore the fearmongering about stress etc.

I think it is the stem trying to sprout extra roots. Likeky with it being wet regularly. It's nothing to worry about. When I grow in coco the same thing happens at times.

nothing to worry about. visible symptoms a "woody" stem is possible low S. Rusty/corky is possibly low B (more likely pH/nute lockout when dealing with trace element visible symptoms) i don't think this is either. If shielded from light and humid could be initial stages of root growth that inevitably air prunes itself. That's not made up off the top of my head, btw. "Root initials" can occur above ground for the reasons stated above - low light / humid. they are harmless.