Is this rusty patch on my bulbo of any concern or sunlight related?

[judyzhusf]

Noticed this recently on an emerging leaf, and as it got bigger the rusty patch also got a little bigger. Its situation right on a eastern window.

[estación seca]

With spots on a Bulbo you always need to look for pests like mealy bug, scale and spider mites. You might need a magnifying glass.

If it's not pests, the problem is usually either sunburn or not enough water. The sun is lowering in the Northern Hemisphere and it might be getting more sun than previously.

Most Bulbos prefer to stay very wet. If they dry too much they can get spots like this.