Den Spectabile has dots on the leaves
 

Recently, my den spectabile has dots spreading on the leaves all over the plant. What’s the possible problem? It always had a little bit dots but didn’t spread until this winter. The new cane is taller but the leaves started to get infected too.

I'm not sure I'd worry about that. Mine looks similarly funky. The only thing I see is your leaf tips seemnto indicate it needs more water (and flush it well). They like water and mine has entered it's growing season.

Great to know that it may not significant problem! I will move to a sunny spot and water it more often! I hope it can bloom soon!

I have found they will soak up almost all the sun and water you can give them during the growing season (mine are starting now). Stop the fertilizer in the fall.