I mean, it is not certain that the antipsychotics are causing the blocked nose, but on the other hand it is entirely plausible that the blockage of adrenergic receptors is having a congestant effect.
Did you increase your dose recently? Maybe the congestion will subside after a while once your body gets used to the new dose.
But maybe there is another reason... I recently had a similar issue with nasal congestion, and eventually realized it may be related to house dust mites, and decided to change my bed linens more often (and wash them at a higher temperature), which seems to have worked.
For the time being, you could try a nasal spray or a decongestant like sudafed (unless the antipsychotics outcompete these drugs at the adrenergic receptors), but of course the issue with those is that once you build a tolerance, discontinuation results in rebound nasal congestion.