Are we talking about your common bleeding heart, Dicentra spectabilis, or hardy fuchsias? If the dicentra, this can indeed become a large plant in time, but is particularly adapted to drier shade, so I doubt that is the reason for yours lankiness and collapsing. More likely just a reaction to the rather heavy rainfall we have experienced periodically over the last few weeks, although a client's dicentra I saw yesterday was majestic in full bloom at about 3' by 4' and showed no effect of rain damage. Staking may be appropriate for these. Pruning per se is not generally a solution for perennials in the peak of their bloom sequence, but can certainly be used to remove any damaged portions. I wouldn't be overly concerned about the hollow stems.

Kerria is a woody shrub and rainfall should not be an issue. It is by nature very lax and leggy and arching in habit and if in heavy bloom, the weight of the flowers combined with the pressure of the rain could cause even more of a prostrate habit, but it will spring back easily.

FWIW, hardy fuchsias are an entirely separate plant from dicentra/bleeding hearts and tend more towards a woody shrub (specially in our mild PNW climate) than a herbaceous perennial like dicentra. They are unaffected by heavy rainfalls and are only now starting to come back into full leaf.

Bleeding hearts and Zina, last year:

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My other hardy fuschia has not sprouted yet this year.
Last year:

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Has anyone heard of using bleeding hearts in bouquets?

I should add that two years ago the culprit was my cat jumping on them.