Clothing is designed to fit, or conform, to the default figure. Once you've added morphs you'll have to take additional steps to get the clothing to fit. The least costly method is to use the magnets. They do, however, require a certain level of skill. There are other applications that can assist you...
Netherworks Studios has a V3 clothing kit to put the morphs into the clothing
The Tailor (at DAZ) will transfer morphs from your charater to the clothing
Wardrobe Wizard (PhilC.net) will fit any clothing item that has been analyzed to a wider variety of supported figures (in their default or morphed state)
Clothing Converter (DAZ) can also convert a clothing model's obj to fit the new morphed figure.

Note, the Netheworks Studios clothing kit will only move DAZ created morphs into the clothing, if you have created a custom morph, one of the other three methods will be the better solution.

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