Check all your water chemistries. Frozen bloodworm, if leftover and uneaten, can cause acute ammonia/nitrite spiking and your water quality can go downhill fast, causing the fish to clamp.
Also, watch for aggression, especially between the gouramis. My blue gourami constantly chases around my sunset thicklip, and the thicklip will sometimes clamp up in a corner to hide. Any fish that is in a corner, behind decor, clamped, is probably being picked on too much.
But since your problem seems to affect all the fish, I would suspect water chemistry/quality problems first.
~~Colesea